Anastasia Dimick
Presentation
A 65-year-old white male presents with a slowly enlarging, tender 1.5-cm hyperkeratotic erythematous nodule on his left forearm. The patient first noticed the lesion about 3 months ago. He has severe photodamage (atrophic skin with numerous lentigines and senile purpura). Because of his occupation as a farmer, he has a chronic history of significant sun exposure. Previous medical history is significant for actinic keratoses (precancerous skin lesions for squamous cell carcinoma) on the face and hands, which have been treated with liquid nitrogen or cryotherapy (Figure 1). Family history is significant for melanoma in his father.
FIGURE 1 • Actinic keratoses.
Differential Diagnosis
In this clinical context, the most likely diagnosis is squamous cell carcinoma of the skin (Figure 2). Other diagnostic possibilities include basal cell carcinoma (Figure 3), basosquamous cell carcinoma, and melanoma. Clinical features of this lesion that point to squamous cell carcinoma are the erythematous color, the presence of hyperkeratosis or rough crusty skin, and tenderness. Melanomas can be hyperkeratotic in rare instances and sore or pruritic but are typically dark brown or black and asymptomatic. There is an uncommon variant of melanoma called amelanotic, which lacks pigment on clinical exam. These lesions may have a clinical appearance similar to basal cell carcinomas, which are usually pearly pink with telangiectatic vessels. The diagnosis of amelanotic melanoma is virtually always made on histopathologic grounds. Basosquamous cell carcinomas have clinical features of both basal cell carcinomas and squamous cell carcinomas.
FIGURE 2 • Squamous cell carcinoma. (From Goodheart HP, MD. Goodheart’s Photoguide of Common Skin Disorders. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2003, FIGURE 22.10.)
FIGURE 3 • Basal cell carcinoma. (From Goodheart HP, MD. Goodheart’s Photoguide of Common Skin Disorders. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2003, FIGURE 22.17.)
Workup
The patient underwent a cutaneous biopsy in the outpatient clinic. Pathology was consistent with well-differentiated squamous cell carcinoma.
Discussion
Squamous cell carcinoma is the second most common type of skin cancer in the United States. Basal cell carcinoma is the most common type of skin cancer in the United States. Together, these nonmelanoma skin cancers account for over 3 million cases per year. The vast majority of these cancers are caused by ultraviolet light exposure. As the population ages, the incidence is expected to increase. Risk factors for developing skin cancer include previous history of skin cancer, family history of skin cancer, fair skin (Fitzpatrick I [always burns, never tans] and Fitzpatrick II [usually burns, tans with difficulty]), severe sunburn history, excessive occupational or avocational sun exposure, and immunosuppressed state. Patients that have undergone organ transplantation have a significantly higher risk of developing skin cancer, particularly squamous cell carcinoma. Candidates for organ transplantation should receive pretransplant counseling on skin cancer prevention and a complete skin examination to identify and treat any precancerous growths, such as actinic keratoses, and cancerous lesions. Squamous cell carcinomas may also arise in burn scars, chronic ulcers, previously irradiated sites, and certain inflammatory conditions of the skin such as discoid lupus erythematosus or genital lichen sclerosus et atrophicus. Although less common than squamous cell carcinomas induced by ultraviolet radiation, these squamous cell carcinomas tend to have a more malignant course.
Diagnosis and Treatment
The diagnosis of skin cancer is confirmed with a skin biopsy. There are two main histopathologic subtypes of squamous cell carcinoma: well-differentiated and poorly differentiated. In general, the prognostic outcome for well-differentiated squamous cell carcinomas is good, while poorly differentiated squamous cell carcinomas tend to behave aggressively and are more likely to metastasize. In addition, other features associated with increased metastatic potential are tumor diameter greater than 2 cm and tumor depth greater than 2 mm. The overall metastatic rate of solar induced squamous cell carcinoma is <5%. Squamous cell carcinomas of the scalp, ears, and lips have a higher metastatic rate of approximately 10% to 15%. Other squamous cell carcinomas, which behave more aggressively, are those with histologic evidence of perineural invasion. Adjuvant radiation therapy should be considered to lower the risk of metastases of squamous cell carcinomas with perineural invasion.
The mainstay of treatment for squamous cell carcinoma is excision with histopathologic confirmation of clear or negative margins. Unlike melanoma, there are no standardized excisional margins for squamous cell carcinoma. Adequate excisional margins typically range from 4 to 10 mm. Another treatment modality is Mohs micrographic surgery. Mohs micrographic surgery should be considered for squamous cell carcinomas on the face, especially those involving the H-zone (temple, midface, perioral, periorbital and periauricular regions) and neoplasms on the trunk and the extremities, which are larger than 2 cm. Mohs micrographic surgery usually results in the lowest risk of recurrence. Recurrent squamous cell carcinomas should be referred for Mohs micrographic surgery.
Treatment of basal cell carcinoma is similar to squamous cell carcinoma. In addition, electrodesiccation and curettage is an acceptable therapeutic option for small (<2 cm) basal cell carcinomas with nonaggressive histopathologic subtypes on the trunk and extremities. There are different histopathologic subtypes of basal cell carcinomas including superficial, nodular, micronodular, infiltrative, and morpheaform. Micronodular, infiltrative, and morpheaform are considered to be the aggressive growth patterns because they are more likely to recur after treatment because of ill-defined borders. Mohs micrographic surgery is the preferred therapeutic option for these basal cell carcinomas.
After successfully treating the squamous cell carcinoma, further follow-up is warranted. The patient should undergo a complete skin and lymph node examination to ensure that there are no other concerning lesions or lymphadenopathy. In addition, the patient should receive counseling on the importance of performing monthly self–skin examinations and practicing sun safety techniques such as avoiding the sun between the hours of 11 am and 4 pm, wearing sun protective clothing, and applying a broad-spectrum sunscreen with an SPF of 15 or higher.
TAKE HOME POINTS
· Squamous cell carcinoma is the second most common type of skin cancer in the United States.
· The vast majority of these cancers are caused by ultraviolet light exposure.
· The mainstay of treatment for squamous cell carcinoma is excision with histopathologic confirmation of clear or negative margins.
· After successfully treating the squamous cell carcinoma, further follow-up is warranted. The patient should undergo a complete skin and lymph node examination to ensure that there are no other concerning lesions or lymphadenopathy.