Tenosynovial giant cell tumor (TGCT)
TGCT exists in three forms: diffuse, localized, and localized TGCT of tendon sheath:
Tenosynovial giant cell tumor (TGCT) of joints and tendon sheaths: diffuse type (also called pigmented villonodular synovitis [PVNS])
The entire synovium of an affected joint or tendon sheath is involved. It affects individuals in their 30s and 40s with equal sex distribution. Grossly, the synovium is red-brown to mottled orange-yellow and prolific with coarse villi, finer fronds, and diffuse nodularity resembling an Angora rug. It is almost always monoarticular. The most common locations include the knee (80%), hip (15%), and ankle. Swelling and effusion accompanied by moderate discomfort, decreased range of motion, and increased warmth to palpation are typical. Pain is frequently less than anticipated from the degree of swelling.
Localized TGCT of the joint (also called benign giant cell synovioma or localized nodular synovitis)
involves only a portion of a synovial surface in a joint, and the lesion is often pedunculated. It presents with symptoms similar to a loose body. It tends not to be as darkly pigmented and has less villous proliferation than is seen in the diffuse form.
Localized TGCT of the tendon sheath (also called giant cell tumor of tendon sheath or fibroxanthoma of tendon sheath)
This benign condition, which occurs with a slightly increased predilection for females, is second only to the ganglion as a source of localized swelling in the hand and wrist. It occurs less frequently (3% to 10%) in the ankle and foot. These nodular lesions usually occur in association with a tendon sheath (formerly called giant cell tumor of tendon sheath). Excision is curative and recurrences are rare.
Histologically, all three forms of villonodular synovitis are remarkably similar.
Pigmented villonodular synovitis (PVNS; synonym: tenosynovial giant cell tumor of the diffuse type) is a rare benign neoplastic synovial disease with a tendency to local recurrence. Typically, the synovium histologically shows proliferation of mononuclear cells, multinuclear giant cells, macrophages and hemosiderin deposits. The most common sites are the knee, hip, shoulder, ankle, foot or elbow. The findings in ultrasound and MRI are groundbreaking for the diagnosis. In addition to synovial proliferation with joint effusion, hypointense areas are typical in the T1- and T2-weighted sequences, which correspond to hemosiderin deposits. The aim of the treatment is a radical removal of the tumor tissue, arthroscopically or through an open synovectomy. To prevent recurrence, it is worthwhile to connect a radionuclide synoviorthesis. Recurrence rates of 10-15% in the first two years after this combination therapy are reported, which is why follow-up examinations are recommended during this period.