Cytologic findings in tenosynovial giant cell tumors investigated by fine-needle aspiration cytology.

Tenosynovial giant cell tumor is a relatively common benign proliferation affecting the articular and periarticular soft tissues. Cytologic findings on smears obtained by fine-needle aspiration are rather characteristic and include a mixture of oval or polygonal mononuclear cells showing vacuolation and/or pigment deposition along with a population of multinucleated giant cells. Separation from other giant cell lesions including true giant cell tumor of bone, chondroblastoma, aneurysmal bone cyst, and granulomatous inflammation must be made. Careful attention to the cytologic findings and correlation with clinical and radiographic data should result in the appropriate diagnosis of tenosynovial giant cell tumor in most cases.