The differential: Is it a worrisome lesion—or not?
The differential diagnosis of melanoma includes both benign and malignant lesions. Malignant and potentially malignant diagnoses to consider include pigmented basal cell carcinoma, pigmented squamous cell carcinoma, carcinoma metastatic to the skin, and dysplastic nevi.2,3
Benign diagnoses to consider include pigmented seborrheic keratoses, lentigo, pyogenic granuloma, Kaposi sarcoma, cherry angioma, subungual traumatic hematoma, dermatofibroma, and nevi (including blue nevi).2,3
The biopsy is paramount
A diagnosis is established based on the microscopic evaluation of suspicious lesions. Studies suggest that one-third to one-half of melanomas arise from existing nevi, with the remainder developing from previously normal-appearing skin.1,2 Patients with increased numbers of either common or dysplastic nevi are at increased risk of melanoma compared with the general population.4 Historical clues include changes in a lesion’s size, color, or symmetry; new growths; personal or family history of melanoma; and bleeding.
A biopsy for histopathologic evaluation is mandatory when a lesion is suspicious for melanoma. Dermoscopy, which involves a device that magnifies skin lesions, may reveal highly specific dermoscopic features for melanoma that can help in determining the need for biopsy.4
The preferred method for biopsy is complete elliptical excision with 2- to 3-mm margins of normal skin.2,3 However, a deep shave biopsy may also be appropriate, depending upon the clinical situation and physician experience with the technique.4