Abstract

Desmoplastic melanoma (DM) is a rare histologic variant of melanoma, with a wide differential diagnosis list of both benign and malignant entities. DM usually presents as a firm nodule, papule, or plaque, and is often not pigmented. The classic histopathologic findings are described as a paucicellular proliferation of malignant spindled melanocytes with an abundant collagenous/myxoid (“desmoplastic”) stroma. Due to the lack of a characteristic clinical appearance and overlapping histopathologic features, DM is prone to misdiagnosis. A 94-year-old male presented to the surgical oncology clinic with a healing shave biopsy site located on his mid-back, and an outside diagnosis of desmoplastic melanoma. Prior to undergoing a wide local excision of the site, the biopsy slides were requested and reviewed. Upon histopathologic review, a dermal-based spindle cell proliferation with a collagenous and myxoid background was observed. Small lymphoid nodules were also identified intermixed with the spindle cells. Immunohistochemical stains S100 and CD34 were performed, which were both positive in the tumor cells. EMA was negative in the tumor cells. Clinicopathologic correlation strongly supported a diagnosis of neurofibroma over the previously diagnosed desmoplastic melanoma. In this review, we describe a diagnostic pitfall that is of vital clinical importance. Knowledge of this pitfall, as well as other entities mimicking DM, will improve identification, unnecessary treatment, and prevent misdiagnosis.

Financial Disclosure:
No current or relevant financial relationships exist.