Soft Tissue, Giant cell tumour of tendon sheath

Giant cell tumour of tendon sheath (localized type tenosynovial giant cell tumour) is a benign neoplastic growth that usually presents with a firm, slow growing painless mass most often located on the hand, however it can arise on the wrists, ankles, knees and feet. Grossly, this tumor is yellow to brown in color and has a fibrous, white cut surface. It has a well circumscribed lobular configuration with surface clefts. On microscopic examination, this tumor has well demarcated borders and is surrounded by a pseudocapsule. It has a nodular architecture with thin septae of fibrous bands separating the nodules. The nodules are composed of a mixture of epithelioid cells, histiocytes, chronic inflammatory cells and osteoclast-like giant cells. The stroma may be hyalinised with cholesterol clefts. Immunohistochemistry is not necessary for the diagnosis, however the osteoclasts-like giant cells and the smaller histiocytoid cells are highlighted by CD163 and CD68.