Fine-needle aspiration biopsy cytology of giant-cell tumor of tendon sheath.

Localized nodular tenosynovitis, better known as giant-cell tumor of tendon sheath (GCTTS), is a common neoplasm that has a peak incidence in the fourth to sixth decades of life. Few reports exist elucidating the cytologic features of this lesion obtained by fine-needle aspiration biopsy (FNAB). The authors describe five patients, aged 8-50 years, in whom GCTTS was diagnosed by FNAB cytology. In four of the patients, the lesion was excised, and the FNAB diagnosis of GCTTS was confirmed; surgical excision is pending in one patient. A diagnosis of malignancy was not suggested in any of the patients. The tumors were .7-5 cm in greatest dimension. In two patients, GCTTS affected the ankle; the hand was affected in the other three. Aspiration smears were cellular in four cases. All but one case contained several multinucleate osteoclast-type giant cells; in addition, binucleate cells were common. The nongiant cell population was dispersed principally as single cells that had a cytologic appearance mimicking histiocytes and osteoblasts. Anisonucleosis was minimal, and nuclear pleomorphism was distinctly absent in both single and multinucleate cells. Mitotic figures were infrequent, except in one case. The diagnosis of GCTTS can be made or at least strongly suggested using FNAB when the cytologic and clinical features are combined.