Aggressive osteogenic desmoplastic melanoma: a case report

Abstract

A case of an osteogenic desmoplastic melanoma occurring on the sole of the foot of a 60-year-old African American man is described. The tumor measured 4.8 cm in greatest dimension, invaded to a thickness of 2.2 cm and metastasized to four of ten inguinal lymph nodes. The majority of the tumor had a classic desmoplastic phenotype with malignant spindle cells set in a sclerotic and myxoid matrix and foci of lymphocyte aggregation. In other areas, there were thick trabeculae of bone rimmed by malignant epithelioid melanocytes. There was a markedly atypical lentiginous hyperplasia in the overlying epidermis. Imaging showed no continuity with the underlying calcaneus. The tumor was characterized immunohistochemically by S100 positivity. Pathologists should be aware of this diagnosis and should differentiate it from osteosarcoma.