Tenosynovial giant cell tumor, localized type (giant cell tumor of tendon sheath)

Tenosynovial giant cell tumor, localized type (giant cell tumor of tendon sheath) is characterized by plump, round histiocytoid cells, multinucleated giant cells, focal xanthomatous change, focal cystic breakdown, hemosiderin deposition, and dense osteoid-like collagenous background. The histiocytoid cells may appear rhabdoid sometimes, often contain hemosiderin in the cytoplasm, may show striking mitotic activity, and are often DESMIN positive. Mitoses do not indicate malignancy!