Fine-needle aspiration diagnosis of psammomatous melanotic schwannoma

A 51-yr-old male presented with an 8-mo history of lower back pain. Compute rized axial tomography (CT) and magnetic resonance imaging (MRI) studies sh owed a 3.5 x 3.0 cm sacral mass within the spinal canal in the region of th e left S2 nerve root. A fine-needle aspirate biopsy (FNAB) was performed un der CT guidance. The cytologic findings included a spindle-cell population with a fibrillary background arranged in a vaguely streaming pattern, wavy nuclei with mild atypia, wispy cytoplasm, rare intranuclear inclusions, and dilated vascular spaces. Some cells contained a nonrefractile granular bro wn pigment consistent with melanin. Also identified were calcified concentr ic laminations typical of psammona bodies. Immunohistochemically, the neopl astic cells were strongly immunoreactive for S-100 protein and HMB-45. A di agnosis of psammomatous melanotic schwannoma was rendered. No stigmata of C arney's complex were identified on physical examination. The patient has de clined the recommendation of surgical excision of the mass. We herein descr ibe a case unequivocally diagnosed as psammomatous melanotic schwannoma by FNAB. (C) Wiley-Liss, Inc.