Husein Husein El-Ahmed, MD

A 73-year-old farmer has a lesion on the dorsum of his right hand that bleeds intermittently. It began 2 years ago as a small itchy papule. It later ulcerated and has gradually increased in size over the past 2 years.

On examination, the lesion is a nontender, ulcerated plaque, 4 cm by 5 cm, with hard and raised edges (Figure 1 and Figure 2) and with evidence of chronic photodamage. No local adenopathy is noted.

Q: Which is the most likely diagnosis?

• Blastomycosis
• Keratoacanthoma
• Basal cell carcinoma
• Squamous cell carcinoma
• Extramammary Paget disease

A: Squamous cell carcinoma is the most likely diagnosis. The lesions may take the form of a patch, plaque, or nodule, sometimes with scaling or an ulcerated center. The borders often are irregular, fleshy, and bleed easily.

Blastomycosis is a rare fungal infection caused by inhaling the spores of the fungus Blastomyces dermatitidis. Skin features begin as papules, pustules, or subcutaneous nodules. Over a period of months, lesions heal to form raised wart-like scars, which are often irreversible.

Keratoacanthoma is a benign nonmelanomatous cancer that grows rapidly and remits spontaneously. This diagnosis is unlikely in our patient, whose lesion evolved over 2 years.

Basal cell carcinoma has a waxy, translucent, or pearly appearance, without a keratotic component. Telangiectasias are common. Unlike squamous cell carcinomas, the edges of basal cell lesions are clear rather than fleshy.

Extramammary Paget disease usually manifests as intense pruritus in affected areas, which appear as chronic intertrigo or nonresolving eczema. The dorsum of the hand is a very rare location for this disease. Given our patient’s presentation, extrammary Paget disease is an unlikely diagnosis.

CHRONIC SUN EXPOSURE IS A KEY RISK FACTOR

Our patient has worked outdoors for many years, and chronic sun exposure is a key risk factor for squamous cell carcinoma.¹

Squamous cell carcinoma is a nonmelanomatous skin cancer arising from the more superficial layers of keratinocytes. Unlike basal cell carcinoma, it can metastasize,² so the diagnosis must be made as soon as possible.

The key to diagnosis is a high degree of suspicion. Patients usually present with chronic sun-damaged skin with lesions as actinic keratoses or keratin horns. Squamous cell carcinoma appears as a thick, adherent scale that does not heal and may intermittently bleed. Because it spreads into the dermis, it can appear like an ulcer, with hard, raised edges, as in our patient.

TREATMENT AND PREVENTION

The standard effective treatment is complete surgical excision.¹ Nonsurgical treatments include curettage plus cautery, cryosurgery, radiotherapy, photodynamic therapy, and imiquimod (Aldara) 5% cream. Minimizing sun exposure and regular checkups are important preventive measures.

Our patient underwent total surgical excision of the lesion. Due to the size of the lesion, a skin graft was required and was obtained from the abdomen. No relapse was observed after 1 year of follow-up.

A 73-year-old farmer has a lesion on the dorsum of his right hand that bleeds intermittently. It began 2 years ago as a small itchy papule. It later ulcerated and has gradually increased in size over the past 2 years.

On examination, the lesion is a nontender, ulcerated plaque, 4 cm by 5 cm, with hard and raised edges (Figure 1 and Figure 2) and with evidence of chronic photodamage. No local adenopathy is noted.

Q: Which is the most likely diagnosis?

• Blastomycosis
• Keratoacanthoma
• Basal cell carcinoma
• Squamous cell carcinoma
• Extramammary Paget disease

A: Squamous cell carcinoma is the most likely diagnosis. The lesions may take the form of a patch, plaque, or nodule, sometimes with scaling or an ulcerated center. The borders often are irregular, fleshy, and bleed easily.

Blastomycosis is a rare fungal infection caused by inhaling the spores of the fungus Blastomyces dermatitidis. Skin features begin as papules, pustules, or subcutaneous nodules. Over a period of months, lesions heal to form raised wart-like scars, which are often irreversible.

Keratoacanthoma is a benign nonmelanomatous cancer that grows rapidly and remits spontaneously. This diagnosis is unlikely in our patient, whose lesion evolved over 2 years.

Basal cell carcinoma has a waxy, translucent, or pearly appearance, without a keratotic component. Telangiectasias are common. Unlike squamous cell carcinomas, the edges of basal cell lesions are clear rather than fleshy.

Extramammary Paget disease usually manifests as intense pruritus in affected areas, which appear as chronic intertrigo or nonresolving eczema. The dorsum of the hand is a very rare location for this disease. Given our patient’s presentation, extrammary Paget disease is an unlikely diagnosis.

CHRONIC SUN EXPOSURE IS A KEY RISK FACTOR

Our patient has worked outdoors for many years, and chronic sun exposure is a key risk factor for squamous cell carcinoma.¹

Squamous cell carcinoma is a nonmelanomatous skin cancer arising from the more superficial layers of keratinocytes. Unlike basal cell carcinoma, it can metastasize,² so the diagnosis must be made as soon as possible.

The key to diagnosis is a high degree of suspicion. Patients usually present with chronic sun-damaged skin with lesions as actinic keratoses or keratin horns. Squamous cell carcinoma appears as a thick, adherent scale that does not heal and may intermittently bleed. Because it spreads into the dermis, it can appear like an ulcer, with hard, raised edges, as in our patient.

TREATMENT AND PREVENTION

The standard effective treatment is complete surgical excision.¹ Nonsurgical treatments include curettage plus cautery, cryosurgery, radiotherapy, photodynamic therapy, and imiquimod (Aldara) 5% cream. Minimizing sun exposure and regular checkups are important preventive measures.

Our patient underwent total surgical excision of the lesion. Due to the size of the lesion, a skin graft was required and was obtained from the abdomen. No relapse was observed after 1 year of follow-up.

A 73-year-old farmer has a lesion on the dorsum of his right hand that bleeds intermittently. It began 2 years ago as a small itchy papule. It later ulcerated and has gradually increased in size over the past 2 years.

On examination, the lesion is a nontender, ulcerated plaque, 4 cm by 5 cm, with hard and raised edges (Figure 1 and Figure 2) and with evidence of chronic photodamage. No local adenopathy is noted.

Q: Which is the most likely diagnosis?

• Blastomycosis
• Keratoacanthoma
• Basal cell carcinoma
• Squamous cell carcinoma
• Extramammary Paget disease

A: Squamous cell carcinoma is the most likely diagnosis. The lesions may take the form of a patch, plaque, or nodule, sometimes with scaling or an ulcerated center. The borders often are irregular, fleshy, and bleed easily.

Blastomycosis is a rare fungal infection caused by inhaling the spores of the fungus Blastomyces dermatitidis. Skin features begin as papules, pustules, or subcutaneous nodules. Over a period of months, lesions heal to form raised wart-like scars, which are often irreversible.

Keratoacanthoma is a benign nonmelanomatous cancer that grows rapidly and remits spontaneously. This diagnosis is unlikely in our patient, whose lesion evolved over 2 years.

Basal cell carcinoma has a waxy, translucent, or pearly appearance, without a keratotic component. Telangiectasias are common. Unlike squamous cell carcinomas, the edges of basal cell lesions are clear rather than fleshy.

Extramammary Paget disease usually manifests as intense pruritus in affected areas, which appear as chronic intertrigo or nonresolving eczema. The dorsum of the hand is a very rare location for this disease. Given our patient’s presentation, extrammary Paget disease is an unlikely diagnosis.

CHRONIC SUN EXPOSURE IS A KEY RISK FACTOR

Our patient has worked outdoors for many years, and chronic sun exposure is a key risk factor for squamous cell carcinoma.¹

Squamous cell carcinoma is a nonmelanomatous skin cancer arising from the more superficial layers of keratinocytes. Unlike basal cell carcinoma, it can metastasize,² so the diagnosis must be made as soon as possible.

The key to diagnosis is a high degree of suspicion. Patients usually present with chronic sun-damaged skin with lesions as actinic keratoses or keratin horns. Squamous cell carcinoma appears as a thick, adherent scale that does not heal and may intermittently bleed. Because it spreads into the dermis, it can appear like an ulcer, with hard, raised edges, as in our patient.

TREATMENT AND PREVENTION

The standard effective treatment is complete surgical excision.¹ Nonsurgical treatments include curettage plus cautery, cryosurgery, radiotherapy, photodynamic therapy, and imiquimod (Aldara) 5% cream. Minimizing sun exposure and regular checkups are important preventive measures.

Our patient underwent total surgical excision of the lesion. Due to the size of the lesion, a skin graft was required and was obtained from the abdomen. No relapse was observed after 1 year of follow-up.

A 46-year-old healthy man presents with a 15-day history of a tender subcutaneous nodule on the dorsum of the right hand that appeared after cleaning his aquarium. He has no fever or systemic symptoms. For 2 weeks he has been taking amoxicillin-clavulanate (Augmentin) and metronidazole (Flagyl), but without an adequate response.

On physical examination, the nodule is painful and has central ulceration (Figure 1). Another two nodules are noted on the forearm, with a sporotrichoid distribution (Figure 2). Locoregional lymph nodes are not palpable.

Laboratory testing (hemography, biochemistry panel, coagulation test, and C-reactive protein) are normal. Routine bacterial cultures of blood and wound drainage are repeatedly negative. Histologic study (Figure 3) reveals signs of acute and chronic inflammation (a mixed infiltrate with lymphocytes, neutrophils, and histiocytes) with abundant bacilli by Ziehl-Neelsen and Giemsa stains.

Q: Which is the most likely diagnosis?

• Tuberculosis verrucosa cutis
• Sporotrichosis
• Nontuberculous mycobacterial infection
• Leishmaniasis
• Nocardiosis

A: The correct answer is nontuberculous mycobacterial infection. Mycobacterium marinum was subsequently isolated from culture (Löwenstein-Jensen medium) of wound drainage.

Tuberculosis verrucosa cutis is an indolent, warty plaque that occurs after direct inoculation of M tuberculosis into the skin of someone previously infected with M tuberculosis. It can result from accidental exposure to tuberculous tissue in high-risk groups such as laboratory workers, physicians, and pathologists.

Sporothrix schenckii is the dimorphic fungus that causes sporotrichosis. Activities associated with acquisition of sporotrichosis include gardening (rose-gardener's disease), landscaping, farming, berry-picking, horticulture, and carpentry. The characteristic infection involves suppurating subcutaneous nodules that progress proximally along lymphatic channels (lymphocutaneous sporotrichosis).

Leishmaniasis is a disease caused by the protozoa of the Leishmania species, which is transmitted by the bite of a female sandfly. Initially, the lesion is a small, red papule up to 2 cm in diameter. Over several weeks, the papule becomes darker, develops a crust in the center, and eventually ulcerates to present a typical appearance of an ulcer with raised edges and surrounding dusky red skin.

Nocardia is a genus of filamentous grampositive bacteria that stains acid-fast, just as M marinum does. Nocardia asteroides primarily affects the lungs and can disseminate systemically. However, Nocardia brasiliensis is often associated with sporotrichoid-spreading subcutaneous nodules.

CLINICAL PRESENTATION AND DIAGNOSIS

M marinum is a genus of nontuberculous mycobacteria that usually causes disease in fish but can cause human skin infection by penetrating through a break in the skin. It can spread to deeper structures, resulting in tenosynovitis, arthritis, or osteomyelitis.¹ The disease caused by M marinum is sometimes called “swimming pool granuloma” or “fish-tank granuloma.”²

In this case, the patient probably acquired the infection while cleaning his home aquarium,³ so asking about contact with pet fish is very important for the clinical diagnosis.

Lesions are usually localized to the site of the inoculation, with a predilection for areas predisposed to trauma, such as the hands and the fingers, after an incubation period of 2 to 8 weeks. Lesions are self-limited and usually appear as pruriginous bluish-red papules or pustules that may increase in size to form a verrucous or violaceous plaque or nodule. Superficial lesions often undergo central ulceration. Disseminated infection is rare and occurs mainly in patients who are immunocompromised because of renal transplant, systemic lupus erythematosus, chronic steroid therapy, or anti-tumor necrosis factor alpha therapy.⁴ In such cases, infection can be life-threatening.

On histopathologic study, a nonspecific inflammation consisting of a mixed infiltrate with lymphocytes, neutrophils, and histiocytes is usually observed. Sometimes a granulomatous inflammatory infiltrate mimicking tuberculoid granuloma may be noted. M marinum is an aerobic, nonmotile acid-fast bacillus. It grows at 30°C to 32°C on Löwenstein-Jensen medium in 2 to 5 weeks, but cultures are rarely positive. Polymerase chain reaction and enzyme-linked immunosorbent assays can help identify the organism. Other diagnoses to be considered are leishmaniasis, tuberculosis verrucosa cutis, blastomycosis, histoplasmosis, and sporotrichosis.

TREATMENT

Treatment of M marinum infection is not based on any specific criteria. Spontaneous resolution in 24 to 36 months has been described. ⁵ Antibiotics are the first-line therapy, and sometimes surgical treatment may be necessary for deeper infection with necrotic tissue. Cryotherapy, electrode therapy, and irradiation have been reported to be effective.

Few studies have been conducted to determine the first-line antibiotic treatment for M marinum infection. In this case, treatment with sulfamethoxazole-trimethoprim⁶ (Bactrim) resulted in resolution of the lesions in 6 months. Other antibiotics often used as monotherapy are tetracycline, minocycline (Minocin), and doxycycline (Vibramycin) 100 mg twice daily for 3 months.⁷ However, treatment failure has been described with many antibiotics.

Multidrug therapy is usually prescribed to minimize the risk of resistance. A combination of clarithromycin (Biaxin), streptomycin, and ethionamide (Trecator) has been prescribed successfully.³ Another combined regimen—clarithromycin 500 mg twice a day, rifampin (Rifadin) 600 mg daily, and ethambutol (Myambutol) 25 mg/kg daily—has been shown to be effective.⁵ Also, rifampin 600 mg daily and ethambutol 15 to 25 mg/kg/day were effective in a patient with a sporotrichoid M marinum infection associated with infliximab (Remicade). ⁸ The duration of treatment ranged between 2 and 6 months, or up to 2 months after the disappearance of the cutaneous lesions.

Clinical awareness of M marinum infection is important so that the diagnosis can be made and appropriate therapy can be initiated promptly, because some cases with disseminated disease and serious complications have been described.⁹

A 46-year-old healthy man presents with a 15-day history of a tender subcutaneous nodule on the dorsum of the right hand that appeared after cleaning his aquarium. He has no fever or systemic symptoms. For 2 weeks he has been taking amoxicillin-clavulanate (Augmentin) and metronidazole (Flagyl), but without an adequate response.

On physical examination, the nodule is painful and has central ulceration (Figure 1). Another two nodules are noted on the forearm, with a sporotrichoid distribution (Figure 2). Locoregional lymph nodes are not palpable.

Laboratory testing (hemography, biochemistry panel, coagulation test, and C-reactive protein) are normal. Routine bacterial cultures of blood and wound drainage are repeatedly negative. Histologic study (Figure 3) reveals signs of acute and chronic inflammation (a mixed infiltrate with lymphocytes, neutrophils, and histiocytes) with abundant bacilli by Ziehl-Neelsen and Giemsa stains.

Q: Which is the most likely diagnosis?

• Tuberculosis verrucosa cutis
• Sporotrichosis
• Nontuberculous mycobacterial infection
• Leishmaniasis
• Nocardiosis

A: The correct answer is nontuberculous mycobacterial infection. Mycobacterium marinum was subsequently isolated from culture (Löwenstein-Jensen medium) of wound drainage.

Tuberculosis verrucosa cutis is an indolent, warty plaque that occurs after direct inoculation of M tuberculosis into the skin of someone previously infected with M tuberculosis. It can result from accidental exposure to tuberculous tissue in high-risk groups such as laboratory workers, physicians, and pathologists.

Sporothrix schenckii is the dimorphic fungus that causes sporotrichosis. Activities associated with acquisition of sporotrichosis include gardening (rose-gardener's disease), landscaping, farming, berry-picking, horticulture, and carpentry. The characteristic infection involves suppurating subcutaneous nodules that progress proximally along lymphatic channels (lymphocutaneous sporotrichosis).

Leishmaniasis is a disease caused by the protozoa of the Leishmania species, which is transmitted by the bite of a female sandfly. Initially, the lesion is a small, red papule up to 2 cm in diameter. Over several weeks, the papule becomes darker, develops a crust in the center, and eventually ulcerates to present a typical appearance of an ulcer with raised edges and surrounding dusky red skin.

Nocardia is a genus of filamentous grampositive bacteria that stains acid-fast, just as M marinum does. Nocardia asteroides primarily affects the lungs and can disseminate systemically. However, Nocardia brasiliensis is often associated with sporotrichoid-spreading subcutaneous nodules.

CLINICAL PRESENTATION AND DIAGNOSIS

M marinum is a genus of nontuberculous mycobacteria that usually causes disease in fish but can cause human skin infection by penetrating through a break in the skin. It can spread to deeper structures, resulting in tenosynovitis, arthritis, or osteomyelitis.¹ The disease caused by M marinum is sometimes called “swimming pool granuloma” or “fish-tank granuloma.”²

In this case, the patient probably acquired the infection while cleaning his home aquarium,³ so asking about contact with pet fish is very important for the clinical diagnosis.

Lesions are usually localized to the site of the inoculation, with a predilection for areas predisposed to trauma, such as the hands and the fingers, after an incubation period of 2 to 8 weeks. Lesions are self-limited and usually appear as pruriginous bluish-red papules or pustules that may increase in size to form a verrucous or violaceous plaque or nodule. Superficial lesions often undergo central ulceration. Disseminated infection is rare and occurs mainly in patients who are immunocompromised because of renal transplant, systemic lupus erythematosus, chronic steroid therapy, or anti-tumor necrosis factor alpha therapy.⁴ In such cases, infection can be life-threatening.

On histopathologic study, a nonspecific inflammation consisting of a mixed infiltrate with lymphocytes, neutrophils, and histiocytes is usually observed. Sometimes a granulomatous inflammatory infiltrate mimicking tuberculoid granuloma may be noted. M marinum is an aerobic, nonmotile acid-fast bacillus. It grows at 30°C to 32°C on Löwenstein-Jensen medium in 2 to 5 weeks, but cultures are rarely positive. Polymerase chain reaction and enzyme-linked immunosorbent assays can help identify the organism. Other diagnoses to be considered are leishmaniasis, tuberculosis verrucosa cutis, blastomycosis, histoplasmosis, and sporotrichosis.

TREATMENT

Treatment of M marinum infection is not based on any specific criteria. Spontaneous resolution in 24 to 36 months has been described. ⁵ Antibiotics are the first-line therapy, and sometimes surgical treatment may be necessary for deeper infection with necrotic tissue. Cryotherapy, electrode therapy, and irradiation have been reported to be effective.

Few studies have been conducted to determine the first-line antibiotic treatment for M marinum infection. In this case, treatment with sulfamethoxazole-trimethoprim⁶ (Bactrim) resulted in resolution of the lesions in 6 months. Other antibiotics often used as monotherapy are tetracycline, minocycline (Minocin), and doxycycline (Vibramycin) 100 mg twice daily for 3 months.⁷ However, treatment failure has been described with many antibiotics.

Multidrug therapy is usually prescribed to minimize the risk of resistance. A combination of clarithromycin (Biaxin), streptomycin, and ethionamide (Trecator) has been prescribed successfully.³ Another combined regimen—clarithromycin 500 mg twice a day, rifampin (Rifadin) 600 mg daily, and ethambutol (Myambutol) 25 mg/kg daily—has been shown to be effective.⁵ Also, rifampin 600 mg daily and ethambutol 15 to 25 mg/kg/day were effective in a patient with a sporotrichoid M marinum infection associated with infliximab (Remicade). ⁸ The duration of treatment ranged between 2 and 6 months, or up to 2 months after the disappearance of the cutaneous lesions.

Clinical awareness of M marinum infection is important so that the diagnosis can be made and appropriate therapy can be initiated promptly, because some cases with disseminated disease and serious complications have been described.⁹

A 46-year-old healthy man presents with a 15-day history of a tender subcutaneous nodule on the dorsum of the right hand that appeared after cleaning his aquarium. He has no fever or systemic symptoms. For 2 weeks he has been taking amoxicillin-clavulanate (Augmentin) and metronidazole (Flagyl), but without an adequate response.

On physical examination, the nodule is painful and has central ulceration (Figure 1). Another two nodules are noted on the forearm, with a sporotrichoid distribution (Figure 2). Locoregional lymph nodes are not palpable.

Laboratory testing (hemography, biochemistry panel, coagulation test, and C-reactive protein) are normal. Routine bacterial cultures of blood and wound drainage are repeatedly negative. Histologic study (Figure 3) reveals signs of acute and chronic inflammation (a mixed infiltrate with lymphocytes, neutrophils, and histiocytes) with abundant bacilli by Ziehl-Neelsen and Giemsa stains.

Q: Which is the most likely diagnosis?

• Tuberculosis verrucosa cutis
• Sporotrichosis
• Nontuberculous mycobacterial infection
• Leishmaniasis
• Nocardiosis

A: The correct answer is nontuberculous mycobacterial infection. Mycobacterium marinum was subsequently isolated from culture (Löwenstein-Jensen medium) of wound drainage.

Tuberculosis verrucosa cutis is an indolent, warty plaque that occurs after direct inoculation of M tuberculosis into the skin of someone previously infected with M tuberculosis. It can result from accidental exposure to tuberculous tissue in high-risk groups such as laboratory workers, physicians, and pathologists.

Sporothrix schenckii is the dimorphic fungus that causes sporotrichosis. Activities associated with acquisition of sporotrichosis include gardening (rose-gardener's disease), landscaping, farming, berry-picking, horticulture, and carpentry. The characteristic infection involves suppurating subcutaneous nodules that progress proximally along lymphatic channels (lymphocutaneous sporotrichosis).

Leishmaniasis is a disease caused by the protozoa of the Leishmania species, which is transmitted by the bite of a female sandfly. Initially, the lesion is a small, red papule up to 2 cm in diameter. Over several weeks, the papule becomes darker, develops a crust in the center, and eventually ulcerates to present a typical appearance of an ulcer with raised edges and surrounding dusky red skin.

Nocardia is a genus of filamentous grampositive bacteria that stains acid-fast, just as M marinum does. Nocardia asteroides primarily affects the lungs and can disseminate systemically. However, Nocardia brasiliensis is often associated with sporotrichoid-spreading subcutaneous nodules.

CLINICAL PRESENTATION AND DIAGNOSIS

M marinum is a genus of nontuberculous mycobacteria that usually causes disease in fish but can cause human skin infection by penetrating through a break in the skin. It can spread to deeper structures, resulting in tenosynovitis, arthritis, or osteomyelitis.¹ The disease caused by M marinum is sometimes called “swimming pool granuloma” or “fish-tank granuloma.”²

In this case, the patient probably acquired the infection while cleaning his home aquarium,³ so asking about contact with pet fish is very important for the clinical diagnosis.

Lesions are usually localized to the site of the inoculation, with a predilection for areas predisposed to trauma, such as the hands and the fingers, after an incubation period of 2 to 8 weeks. Lesions are self-limited and usually appear as pruriginous bluish-red papules or pustules that may increase in size to form a verrucous or violaceous plaque or nodule. Superficial lesions often undergo central ulceration. Disseminated infection is rare and occurs mainly in patients who are immunocompromised because of renal transplant, systemic lupus erythematosus, chronic steroid therapy, or anti-tumor necrosis factor alpha therapy.⁴ In such cases, infection can be life-threatening.

On histopathologic study, a nonspecific inflammation consisting of a mixed infiltrate with lymphocytes, neutrophils, and histiocytes is usually observed. Sometimes a granulomatous inflammatory infiltrate mimicking tuberculoid granuloma may be noted. M marinum is an aerobic, nonmotile acid-fast bacillus. It grows at 30°C to 32°C on Löwenstein-Jensen medium in 2 to 5 weeks, but cultures are rarely positive. Polymerase chain reaction and enzyme-linked immunosorbent assays can help identify the organism. Other diagnoses to be considered are leishmaniasis, tuberculosis verrucosa cutis, blastomycosis, histoplasmosis, and sporotrichosis.

TREATMENT

Treatment of M marinum infection is not based on any specific criteria. Spontaneous resolution in 24 to 36 months has been described. ⁵ Antibiotics are the first-line therapy, and sometimes surgical treatment may be necessary for deeper infection with necrotic tissue. Cryotherapy, electrode therapy, and irradiation have been reported to be effective.

Few studies have been conducted to determine the first-line antibiotic treatment for M marinum infection. In this case, treatment with sulfamethoxazole-trimethoprim⁶ (Bactrim) resulted in resolution of the lesions in 6 months. Other antibiotics often used as monotherapy are tetracycline, minocycline (Minocin), and doxycycline (Vibramycin) 100 mg twice daily for 3 months.⁷ However, treatment failure has been described with many antibiotics.

Multidrug therapy is usually prescribed to minimize the risk of resistance. A combination of clarithromycin (Biaxin), streptomycin, and ethionamide (Trecator) has been prescribed successfully.³ Another combined regimen—clarithromycin 500 mg twice a day, rifampin (Rifadin) 600 mg daily, and ethambutol (Myambutol) 25 mg/kg daily—has been shown to be effective.⁵ Also, rifampin 600 mg daily and ethambutol 15 to 25 mg/kg/day were effective in a patient with a sporotrichoid M marinum infection associated with infliximab (Remicade). ⁸ The duration of treatment ranged between 2 and 6 months, or up to 2 months after the disappearance of the cutaneous lesions.

Clinical awareness of M marinum infection is important so that the diagnosis can be made and appropriate therapy can be initiated promptly, because some cases with disseminated disease and serious complications have been described.⁹

A healthy 68-year-old farmer presents with an asymptomatic skin lesion on his right arm that appeared spontaneously without trauma or bite 5 months ago and has grown progressively since then.

On examination, he has an erythematous plaque that has an elevated edge, a central depression, and a hard consistency (Figure 1). The sensitivity of the lesion is preserved, and no thickened nerves are observed. Local and regional lymph nodes are not palpable. Basic biochemical and blood serologic tests reveal no significant abnormalities.

Q: Which is the most likely diagnosis?

• Squamous cell carcinoma
• Cutaneous lymphoma
• Cutaneous mycobacteriosis
• Sarcoidosis
• Lichen planus

A: The patient has squamous cell carcinoma. Histopathologic examination of biopsy samples from the lesion showed atypical keratinocytes extending from the epidermis to the dermis, compatible with this diagnosis (Figure 2).

As for the other possibilities:

Cutaneous lymphoma, characterized by atypical proliferation of T or B lymphocytes in the skin, usually presents as a slow-growing indurated nodule or plaque.

Cutaneous mycobacteriosis is caused by infection with Mycobacterium tuberculosis, M leprae, or M marinum. Caseous granulomas are often found on histopathologic study, but special culture and polymerase chain reaction tests are necessary for the diagnosis. Clinically, the lesion is an indurated nodule or plaque that grows slowly, with decreased sensitivity in the case of leprosy, and with a sporotrichoid pattern in the case of M marinum infection.

Our patient underwent a tuberculin skin test, which was negative, as were polymerase chain reaction testing and culture of the biopsy material for mycobacteria.

Sarcoidosis is a systemic disease of unknown cause characterized by noncaseous granulomas in the lungs, mediastinum, lymph nodes, or other sites.¹ Cutaneous involvement includes nonspecific clinical forms (eg, nodosum erythema) and other more specific forms (eg, maculopapular, subcutaneous, cicatricial, or lupus pernio variants). This patient has no granulomas on skin biopsy.

Lichen planus is a chronic inflammatory disease of unknown cause that affects the skin, genitalia, mucous membranes, or appendages. It appears as pruritic purple polygonal papules with Wickham striae, usually affecting the wrists and ankles.

A COMMON FORM OF SKIN CANCER

Squamous cell carcinoma and basal cell carcinoma account for 95% of cases of nonmelanomatous skin cancer, and the incidence of squamous cell carcinoma has been increasing.

Long-term exposure to ultraviolet radiation (ie, sunlight), often related to occupation, is the most common cause of squamous cell carcinoma. Other risk factors include thermal injury or burns, ionizing radiation, human papilloma virus infection, immunosuppressive therapy (eg, after organ transplantation²), exposure to chemical carcinogens, and diseases such as xeroderma pigmentosum or oculocutaneous albinism. Unlike basal cell carcinoma, which usually arises de novo, squamous cell carcinoma often arises from precursor lesions, such as actinic keratosis and Bowen disease.

Squamous cell carcinoma commonly manifests as shallow ulcers, often with a keratinous crust and an elevated, indurated border, but also as plaques or nodules, as in this patient. Incipient lesions present as erythematous, firm, keratotic papules, but the lesions on sun-exposed areas such as the head or neck can be pigmented.

The surrounding skin usually shows changes of actinic damage, usually with ulceration, scaling, crusting, or verrucous appearance. When the lesion presents as an erythematous plaque, as in this patient, mycobacterial infection and cutaneous lymphoma should be ruled out. Histologic studies and culture for mycobacteria are necessary for an acute diagnosis. Other conditions in the differential diagnosis are keratoacanthoma, cutaneous metastasis, and sarcoidosis.

The only way to confirm the diagnosis of squamous cell carcinoma is to obtain a specimen by biopsy or surgical excision. Histologic features include atypical keratinocytes extending from the epidermis to the dermis, with dyskeratosis, intercellular bridges, variable central keratinization, and “horn pearls,” depending on how well or how poorly differentiated the tumor.³ Most squamous cell carcinomas arise in solar keratoses, usually at the periphery of the tumor.

Most squamous cell carcinomas are only locally aggressive. Tumors greater than 5 mm in thickness have a 20% risk of metastasis.

TREATMENT OPTIONS

Surgical excision is the most common treatment. Other options are cryotherapy, topical chemotherapy, curettage and electrodesiccation, radiotherapy, and Mohs micrographic surgery. Photodynamic therapy or imiquimod (Aldara) are used only for noninvasive forms.

The possibility of metastasis should be investigated in cases of extensive squamous cell carcinoma, when mucous membranes are affected, and when squamous cell lesions are poorly differentiated.

Our patient’s tumor was removed, with adequate safety margins in surface and depth, and with dermo-epidermal graft closure. The lesion has not recurred at 9 months of follow-up.

A healthy 68-year-old farmer presents with an asymptomatic skin lesion on his right arm that appeared spontaneously without trauma or bite 5 months ago and has grown progressively since then.

On examination, he has an erythematous plaque that has an elevated edge, a central depression, and a hard consistency (Figure 1). The sensitivity of the lesion is preserved, and no thickened nerves are observed. Local and regional lymph nodes are not palpable. Basic biochemical and blood serologic tests reveal no significant abnormalities.

Q: Which is the most likely diagnosis?

• Squamous cell carcinoma
• Cutaneous lymphoma
• Cutaneous mycobacteriosis
• Sarcoidosis
• Lichen planus

A: The patient has squamous cell carcinoma. Histopathologic examination of biopsy samples from the lesion showed atypical keratinocytes extending from the epidermis to the dermis, compatible with this diagnosis (Figure 2).

As for the other possibilities:

Cutaneous lymphoma, characterized by atypical proliferation of T or B lymphocytes in the skin, usually presents as a slow-growing indurated nodule or plaque.

Cutaneous mycobacteriosis is caused by infection with Mycobacterium tuberculosis, M leprae, or M marinum. Caseous granulomas are often found on histopathologic study, but special culture and polymerase chain reaction tests are necessary for the diagnosis. Clinically, the lesion is an indurated nodule or plaque that grows slowly, with decreased sensitivity in the case of leprosy, and with a sporotrichoid pattern in the case of M marinum infection.

Our patient underwent a tuberculin skin test, which was negative, as were polymerase chain reaction testing and culture of the biopsy material for mycobacteria.

Sarcoidosis is a systemic disease of unknown cause characterized by noncaseous granulomas in the lungs, mediastinum, lymph nodes, or other sites.¹ Cutaneous involvement includes nonspecific clinical forms (eg, nodosum erythema) and other more specific forms (eg, maculopapular, subcutaneous, cicatricial, or lupus pernio variants). This patient has no granulomas on skin biopsy.

Lichen planus is a chronic inflammatory disease of unknown cause that affects the skin, genitalia, mucous membranes, or appendages. It appears as pruritic purple polygonal papules with Wickham striae, usually affecting the wrists and ankles.

A COMMON FORM OF SKIN CANCER

Squamous cell carcinoma and basal cell carcinoma account for 95% of cases of nonmelanomatous skin cancer, and the incidence of squamous cell carcinoma has been increasing.

Long-term exposure to ultraviolet radiation (ie, sunlight), often related to occupation, is the most common cause of squamous cell carcinoma. Other risk factors include thermal injury or burns, ionizing radiation, human papilloma virus infection, immunosuppressive therapy (eg, after organ transplantation²), exposure to chemical carcinogens, and diseases such as xeroderma pigmentosum or oculocutaneous albinism. Unlike basal cell carcinoma, which usually arises de novo, squamous cell carcinoma often arises from precursor lesions, such as actinic keratosis and Bowen disease.

Squamous cell carcinoma commonly manifests as shallow ulcers, often with a keratinous crust and an elevated, indurated border, but also as plaques or nodules, as in this patient. Incipient lesions present as erythematous, firm, keratotic papules, but the lesions on sun-exposed areas such as the head or neck can be pigmented.

The surrounding skin usually shows changes of actinic damage, usually with ulceration, scaling, crusting, or verrucous appearance. When the lesion presents as an erythematous plaque, as in this patient, mycobacterial infection and cutaneous lymphoma should be ruled out. Histologic studies and culture for mycobacteria are necessary for an acute diagnosis. Other conditions in the differential diagnosis are keratoacanthoma, cutaneous metastasis, and sarcoidosis.

The only way to confirm the diagnosis of squamous cell carcinoma is to obtain a specimen by biopsy or surgical excision. Histologic features include atypical keratinocytes extending from the epidermis to the dermis, with dyskeratosis, intercellular bridges, variable central keratinization, and “horn pearls,” depending on how well or how poorly differentiated the tumor.³ Most squamous cell carcinomas arise in solar keratoses, usually at the periphery of the tumor.

Most squamous cell carcinomas are only locally aggressive. Tumors greater than 5 mm in thickness have a 20% risk of metastasis.

TREATMENT OPTIONS

Surgical excision is the most common treatment. Other options are cryotherapy, topical chemotherapy, curettage and electrodesiccation, radiotherapy, and Mohs micrographic surgery. Photodynamic therapy or imiquimod (Aldara) are used only for noninvasive forms.

The possibility of metastasis should be investigated in cases of extensive squamous cell carcinoma, when mucous membranes are affected, and when squamous cell lesions are poorly differentiated.

Our patient’s tumor was removed, with adequate safety margins in surface and depth, and with dermo-epidermal graft closure. The lesion has not recurred at 9 months of follow-up.

A healthy 68-year-old farmer presents with an asymptomatic skin lesion on his right arm that appeared spontaneously without trauma or bite 5 months ago and has grown progressively since then.

On examination, he has an erythematous plaque that has an elevated edge, a central depression, and a hard consistency (Figure 1). The sensitivity of the lesion is preserved, and no thickened nerves are observed. Local and regional lymph nodes are not palpable. Basic biochemical and blood serologic tests reveal no significant abnormalities.

Q: Which is the most likely diagnosis?

• Squamous cell carcinoma
• Cutaneous lymphoma
• Cutaneous mycobacteriosis
• Sarcoidosis
• Lichen planus

A: The patient has squamous cell carcinoma. Histopathologic examination of biopsy samples from the lesion showed atypical keratinocytes extending from the epidermis to the dermis, compatible with this diagnosis (Figure 2).

As for the other possibilities:

Cutaneous lymphoma, characterized by atypical proliferation of T or B lymphocytes in the skin, usually presents as a slow-growing indurated nodule or plaque.

Cutaneous mycobacteriosis is caused by infection with Mycobacterium tuberculosis, M leprae, or M marinum. Caseous granulomas are often found on histopathologic study, but special culture and polymerase chain reaction tests are necessary for the diagnosis. Clinically, the lesion is an indurated nodule or plaque that grows slowly, with decreased sensitivity in the case of leprosy, and with a sporotrichoid pattern in the case of M marinum infection.

Our patient underwent a tuberculin skin test, which was negative, as were polymerase chain reaction testing and culture of the biopsy material for mycobacteria.

Sarcoidosis is a systemic disease of unknown cause characterized by noncaseous granulomas in the lungs, mediastinum, lymph nodes, or other sites.¹ Cutaneous involvement includes nonspecific clinical forms (eg, nodosum erythema) and other more specific forms (eg, maculopapular, subcutaneous, cicatricial, or lupus pernio variants). This patient has no granulomas on skin biopsy.

Lichen planus is a chronic inflammatory disease of unknown cause that affects the skin, genitalia, mucous membranes, or appendages. It appears as pruritic purple polygonal papules with Wickham striae, usually affecting the wrists and ankles.

A COMMON FORM OF SKIN CANCER

Squamous cell carcinoma and basal cell carcinoma account for 95% of cases of nonmelanomatous skin cancer, and the incidence of squamous cell carcinoma has been increasing.

Long-term exposure to ultraviolet radiation (ie, sunlight), often related to occupation, is the most common cause of squamous cell carcinoma. Other risk factors include thermal injury or burns, ionizing radiation, human papilloma virus infection, immunosuppressive therapy (eg, after organ transplantation²), exposure to chemical carcinogens, and diseases such as xeroderma pigmentosum or oculocutaneous albinism. Unlike basal cell carcinoma, which usually arises de novo, squamous cell carcinoma often arises from precursor lesions, such as actinic keratosis and Bowen disease.

Squamous cell carcinoma commonly manifests as shallow ulcers, often with a keratinous crust and an elevated, indurated border, but also as plaques or nodules, as in this patient. Incipient lesions present as erythematous, firm, keratotic papules, but the lesions on sun-exposed areas such as the head or neck can be pigmented.

The surrounding skin usually shows changes of actinic damage, usually with ulceration, scaling, crusting, or verrucous appearance. When the lesion presents as an erythematous plaque, as in this patient, mycobacterial infection and cutaneous lymphoma should be ruled out. Histologic studies and culture for mycobacteria are necessary for an acute diagnosis. Other conditions in the differential diagnosis are keratoacanthoma, cutaneous metastasis, and sarcoidosis.

The only way to confirm the diagnosis of squamous cell carcinoma is to obtain a specimen by biopsy or surgical excision. Histologic features include atypical keratinocytes extending from the epidermis to the dermis, with dyskeratosis, intercellular bridges, variable central keratinization, and “horn pearls,” depending on how well or how poorly differentiated the tumor.³ Most squamous cell carcinomas arise in solar keratoses, usually at the periphery of the tumor.

Most squamous cell carcinomas are only locally aggressive. Tumors greater than 5 mm in thickness have a 20% risk of metastasis.

TREATMENT OPTIONS

Surgical excision is the most common treatment. Other options are cryotherapy, topical chemotherapy, curettage and electrodesiccation, radiotherapy, and Mohs micrographic surgery. Photodynamic therapy or imiquimod (Aldara) are used only for noninvasive forms.

The possibility of metastasis should be investigated in cases of extensive squamous cell carcinoma, when mucous membranes are affected, and when squamous cell lesions are poorly differentiated.

Our patient’s tumor was removed, with adequate safety margins in surface and depth, and with dermo-epidermal graft closure. The lesion has not recurred at 9 months of follow-up.