Giant Cell Tumor of the Tendon Sheath 

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. See the images below.

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.^[1] 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.^{[2, 3, 3]} When the origin of these poorly confined soft-tissue masses is uncertain, Enzinger and Weiss^[4] classify these tumors as the diffuse type of giant cell tumors of the tendon sheath, whether or not they involve the adjacent joint.^[5]

This article focuses on the common localized form of giant cell tumors—that is, the giant cell tumors of the tendon sheath that are often found in the hands and feet.^{[6, 7, 8, 9, 10]}

Giant cell tumors of the tendon sheath are usually painless masses that have been present for a long time. The reported duration of symptoms ranges from weeks to as long as 30 years. These tumors usually cause no symptoms, except for occasional distal numbness; however, mild disability may result from impaired function of the digit secondary to the size of the lesion.

Frequency

Giant cell tumors of the tendon sheath are the second most common tumors in the hand; simple ganglion cysts are the most common. Giant cell tumors of the tendon sheath most commonly occur in patients aged 30-50 years, with a peak incidence in those aged 40-50 years. Rarely are these tumors found in patients younger than 10 years or older than 60 years. The female-to-male ratio is 3:2.

Giant cell tumors of the tendon sheath are associated with degenerative joint disease, especially in the distal interphalangeal (DIP) joint. Jones et al^[11] noted degenerative joint disease in the joint from which a tumor arose or in the joint nearest to the mass in 46 of 91 cases in which radiographs were reviewed. An occasional association with rheumatoid arthritis has been reported;^[12] however, to the authors' knowledge, no pathogenetic relationship between rheumatoid arthritis and giant cell tumor of the tendon sheath has been demonstrated, and their simultaneous occurrence may be coincidental. Antecedent trauma occurs in a variable number of these patients, but its association with these tumors is also probably coincidental.

As is true for most soft-tissue tumors, the etiology of giant cell tumors of the tendon sheath is unknown. Pathogenetic theories have included trauma, disturbed lipid metabolism, osteoclastic proliferation, infection, vascular disturbances, immune mechanisms, inflammation, neoplasia, and metabolic disturbances.^[13] Probably the most widely accepted theory, as Jaffe et al^[14] proposed, is that of a reactive or regenerative hyperplasia associated with an inflammatory process.

Histochemical evidence shows that the mononuclear cells and giant cells present in these lesions resemble osteoclasts,^{[15, 16]} suggesting a bone marrow–derived monocyte/macrophage lineage for these tumors. Recent polymerase chain reaction (PCR) assays have shown that giant cell tumors of the tendon sheath are polyclonal proliferations,^[17] suggesting that these masses are nonneoplastic proliferations, if one accepts the premise that a population of cells forming a tumorous mass must show clonality to be classified as a neoplasm.

Typically, these masses occur along the volar aspect of the hand and fingers and are most commonly adjacent to the DIP joint.^{[18, 19, 20]} Two thirds of these masses are located along the volar aspect of the fingers (see the image below). The index and long fingers are most commonly involved. Despite the prevalence of volar lesions, a dorsal location is not uncommon. A slight predominance for the right hand exists. The second most common site is the toe. Less common sites include extra-articular areas around larger joints, such as the knees, wrists, and ankles.^[21]

See the image below.

Giant cell tumors of the tendon sheath are firm, lobulated, nontender, slow-growing masses that are firmly fixed to the underlying structures. Usually, the overlying skin is freely mobile over proximal masses in the fingers. The skin is adherent to distal tumors. In digital lesions, mild numbness in the distal part of the involved fingertip is occasionally present. The lesion is not transilluminating. (Transillumination is more consistent with a cystic structure.)

The clinical differential diagnosis may include foreign body granuloma, necrobiotic granuloma, tendinous xanthoma,^[22] fibroma of the tendon sheath, infection, ganglion cyst, rheumatoid nodule, epidermoid cyst, lipoma, and a knuckle pad, among other less common entities. Many of these entities can often be excluded with careful history taking and physical examination.

When the pressure of the mass causes cortical erosion or when the mass has intralesional calcification, the radiographic differential diagnosis includes synovial chondromatosis, calcific tendinitis, and periosteal chondroma. Other entities that cannot be excluded on the basis of clinical findings in many cases include fibrokeratoma, myxoid cyst, reticulohistiocytoma, metastasis, and soft-tissue sarcomas (particularly epithelioid sarcoma and synovial sarcoma); these entities can only be definitively distinguished by means of histologic review.

See Workup, Histologic Findings.

A patient's poor medical health and the presence of life-threatening illnesses are contraindications to the surgical resection of these tumors.