Fine-needle aspiration diagnosis of psammomatous melanotic schwannoma.

A 51-yr-old male presented with an 8-mo history of lower back pain. Computerized axial tomography (CT) and magnetic resonance imaging (MRI) studies showed a 3.5 X 3.0 cm sacral mass within the spinal canal in the region of the left S2 nerve root. A fine-needle aspirate biopsy (FNAB) was performed under 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 brown pigment consistent with melanin. Also identified were calcified concentric laminations typical of psammoma bodies. Immunohistochemically, the neoplastic cells were strongly immunoreactive for S-100 protein and HMB-45. A diagnosis of psammomatous melanotic schwannoma was rendered. No stigmata of Carney's complex were identified on physical examination. The patient has declined the recommendation of surgical excision of the mass. We herein describe a case unequivocally diagnosed as psammomatous melanotic schwannoma by FNAB.