Pigmented lesion on the cheek: a quiz.

A white 30-year-old woman presented with a 4-year history of a nodular lesion of the face that appeared to be growing and changing colour. Surgical excision without histolopathoogical examination 3 years previously for the same lesion had resulted in a relapse 3 months later. Physical examination showed a 1.3 cm erythematous, violaceous, multi-lobed tumour, with 2 pigmented satellite nodules on the right cheek (Fig. 1). Its surface was irregular with an infiltrated base extending to the subcutaneous tissue. The lesion was painless. A surgical excision was made with a margin of 3 mm in the macro scopic healthy skin. Pathological examination of the tumours revealed an asymmetrical lesion with dense proliferation of melanocytic cells at the dermal–epidermal junction, with sheets of cells extending deep into the dermis and focally involving the deep margin. The dermal nests lacked maturation with depth. Cellular atypia, with some cells displaying enlarged, hyperchromatic nuclei and prominent nucleoli, and rare deep mitotic figures, were detected. Immunohistochemistry was positive for S-100, HBM-45 and Melan A. What is your diagnosis? See next page for answer.