Fine‐needle aspiration cytology of diffuse type tenosynovial giant cell tumor with malignant trasformation and review of literature

Abstract

Tenosynovial giant cell tumors (TGCTs) arise from the synovium of joint, bursa, and tendon sheath. Diffuse type often affects large joints, has higher recurrence rates, metastases, and malignant transformation potential compared to the localized type. The cytopathology of TGCT, a fibrohistiocytic neoplasm distinct from other giant cell–rich soft tissue tumors, is rarely reported. Here we describe cytomorphology of a case of TGCT that was initially diagnosed on fine‐needle aspiration cytology (FNAC) consisting of a mixture of singly scattered polygonal or spindle mononuclear cells with hemosiderin laden macrophages, inflammatory cells, and a population of multinucleated osteoclast‐like giant cells. Persistent symptoms and repeat excision were consistent with high‐grade malignant transformation of the TGCT. Atypical cytologic features in a recurrent, infiltrative, or a metastatic lesion should raise suspicion for malignancy.