An 88-year-old woman presented for a periodic total body skin exam. Her history included basal cell carcinoma and melanoma.
Key point: During the exam, an irregularly pigmented lesion was noted on the upper right arm. The lesion was non-tender and non-pruritic. The differential diagnosis primarily revolved around dysplastic nevus and melanoma. However, a biopsy showed heavily pigmented squamous cell carcinoma in situ.
Treatment: The lesion was completely excised.
Note: The actual diagnosis was surprising. Nonetheless, eccentric and irregular pigmentation in a skin lesion should prompt consideration for a biopsy.