Giant Cell Tumor Of Soft Tissue

Not clinically relevant

Giant cell tumor of soft tissue lacks the mutations of the H3-3A (H3F3A) gene that are present in the vast majority of giant cell tumors of bone, suggesting a different pathogenesis.

Tumors range in size from 0.7 to 10 cm (mean: 3 cm). Subcutaneous adipose tissue or dermis is involved in 70% of tumors; 30% are situated deep to superficial fascia. Giant cell tumor of soft tissue is a well-circumscribed, mostly solid, nodular mass with a fleshy, reddish-brown or gray cut surface. Gritty regions of mineralized bone are frequently present at the periphery.

Giant cell tumor of soft tissue displays a multinodular architecture (85%). Cellular nodules are separated by fibrous septa of varying thickness, containing haemosiderin-laden macrophages. The nodules are composed of a mixture of round to oval mononuclear cells and osteoclast-like multinucleated giant cells, with both cell types immersed in a richly vascularized stroma. Mitotic activity is readily seen in giant cell tumor of soft tissue. Nuclear pleomorphism and bizarre giant cells are absent, and necrosis is rarely found. Metaplastic bone formation is present in approximately 50% of tumors, most often in the form of a peripheral shell of woven bone. Aneurysmal bone cyst–like changes may be seen. Vascular invasion is identified in about 30% of tumors. Additional histological features include stromal hemorrhage (50%) and regressive changes in the form of marked stromal fibrosis and clusters of foamy macrophages (70%). Immunohistochemistry is not helpful.

Not clinically relevant

Giant cell tumor of soft tissue is associated with a local recurrence rate of 12%, with very rare metastasis.

Not clinically relevant

Essential: multinodular superficial soft tissue neoplasm; histiocytoid mononuclear cell population with osteoclastic giant cells; haemosiderin deposition and metaplastic bone formation are commonly observed.