Malignant peripheral nerve sheath tumor: a fine-needle aspiration biopsy study.

Although the histopathologic features of malignant peripheral nerve sheath tumors (MPNST) have been well-described, the cytologic features are less well-characterized. We retrospectively reviewed 4 aspiration specimens from 3 patients with histologically-proven MPNST. The biopsy specimens were obtained from the primary tumor (1 case), a local recurrence (2 cases), and a pulmonary metastasis (1 case). The patients were women, aged 42, 61, and 70 yr. The primary tumors arose from the left neck and elbow, and from a neurofibroma in the right medial thigh. The latter patient had von Recklinghausen's disease. Cardinal cytomorphologic features included aggregates and single cells with ovoid to elongated, and comma to serpentine shapes, as well as hyperchromatic nuclei surrounded by delicate, tapering cytoplasm. Nuclear pleomorphism ranged from slight to marked. Multinucleated giant cells were seen in 2 cases. In general, the degree of nuclear variability within each individual case exceeded that typically observed with synovial sarcoma or fibrosarcoma. Although the cytomorphologic features may strongly suggest MPNST, clinical correlation is necessary and immunocytochemistry (i.e., S-100 protein) may help to distinguish MPNST from other spindle-cell sarcomas. Origin from a nerve trunk or preexisting neurofibroma, or occurrence in a patient with von Recklinghausen's disease, confirms the diagnosis of MPNST.