EPITHELIOID PSAMMOMATOUS MELANOTIC SCHWANNOMA WITH OSSEOUS METAPLASIA

Psammomatous melanotic schwannoma is a very rare soft tissue neoplasm, which is clinically, biologically, and histologically distinct from c onventional schwannoma. A significant proportion of patients may prese nt with Carney's heritable complex of myxomas, spotty pigmentation, an d endocrine overactivity. Typically, the lesion is composed of spindle d and epithelioid cells displaying abundant intracytoplasmic melanin p igment, together with the formation of psammoma bodies. We report an e pithelioid example of this tumor arising in the anterior abdominal wal l of a 23-year-old man. A unique feature was a peripheral rim of osseo us metaplasia. The tumor was erroneously diagnosed as a metastatic mal ignant melanoma on initial examination owing to its immunohistochemica l coexpression of S100 protein and HMB-45. Psammoma bodies have not to our knowledge been described in melanomas, and their presence serves as a useful clue to the diagnosis of psammomatous melanotic schwannoma .