Tenosynovial giant cell tumor with extensive myxoid change: A rare variant of a common tumor

Tenosynovial giant cell tumor is a common tumor of synovial origin that usually occurs between the ages of 30 and 50 years. It is classified into localized and diffuse types based on the presence of a capsule around the lesion. Histologically, it is characterized by scattered large epithelioid cells with eosinophilic cytoplasm and eccentric nuclei, histiocytoid cells, multinucleated osteoclast-like giant cells, and varying amounts of hemosiderin deposition. Prominent myxoid stroma is a very rare finding in this tumor. We report the case of a 35-year-old woman with tenosynovial giant cell tumor, whereby otherwise typical cells are set in a predominant loose myxoid stroma. This morphology is important to recognize, as it can closely mimic other soft tissue tumors with a predominant myxoid matrix.