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Giant cell tumors of the tendon sheath are the second most common tumors of the hand, with simple ganglion cysts being the most common. Chassaignac first described these benign soft-tissue masses in 1852, and he overstated their biologic potential in referring to them as cancers of the tendon sheath.
Giant cell tumors of the soft tissue are classified into 2 types: the common localized type and the rare diffuse type. The rare diffuse form is considered the soft tissue counterpart of diffuse pigmented villonodular synovitis (PVNS) and typically affects the lower extremities. Its anatomic distribution parallels that of PVNS, with lesions most commonly found around the knee, followed by the ankle and foot; however, the diffuse form occasionally affects the hand. Typically, these lesions, like those of PVNS, occur in young patients; 50% of cases are diagnosed in patients younger than 40 years. The diffuse form is often locally aggressive, and multiple recurrences after excision are common.
Because of the similarities in age, tumor locations, clinical presentations, and symptoms for patients with PVNS and patients with the diffuse form of giant cell tumors of the tendon sheath, the diffuse form probably represents an extra-articular extension of a primary intra-articular PVNS process. Findings from flow cytometric DNA analysis suggest that PVNS and giant cell tumors of the tendon sheath are histopathologically similar but clinically distinct lesions. When the origin of these poorly confined soft-tissue masses is uncertain, Enzinger and Weiss (1995) classify these tumors as the diffuse type of giant cell tumors of the tendon sheath, whether or not they involve the adjacent joint.
Malignant Giant Cell Tumor of the Tendon Sheath
