Psammomatous melanotic schwannoma. A distinctive, heritable tumor with special associations, including cardiac myxoma and the Cushing syndrome

Abstract

Schwannoma, a benign tumor of peripheral nerve sheath, infrequently contains melanin and even less frequently features psammoma bodies. Forty schwannomas that displayed both findings were obtained from 31 patients, aged 10 to 63 years. Seventeen patients (55%) had the complex of myxomas, spotty pigmentation, and endocrine overactivity, a familial syndrome. Six (19%) had multiple tumors. Tumor sites included posterior spinal nerve roots (11 tumors), alimentary tract (11 tumors), and bone (three tumors). Two-thirds of the neoplasms caused symptoms. Grossly, the tumors were black, brown, or blue, encapsulated, and solid or spongy. Microscopically, they were circumscribed but incompletely encapsulated; they contained spindle and epithelioid cells, melanin, psammoma bodies, and fat. The spindle cells were arranged in interlacing fascicles, and exhibited whorling and occasional nuclear palisading. Immunostaining revealed that the tumors were positive for S-100 protein and vimentin and negative for glial fibrillary acidic protein, actin, and keratin. Ultrastructurally, the cells features elongated processes, continuous basal lamina, melanosomes, and intercellular long-spacing collagen. Twenty-one patients (68%) were alive without evidence of the neoplasm; two of these each had two local recurrences. Seven patients died, three (10%) as a result of metastasis. Three patients were lost to follow-up.