We regard the giant cell tumors of the tendons and tendon sheaths as true blastomatous formations of well differentiated elements of osteoperiosteal and histocytitary origin. The said differentiation sometimes allows the formation of an osteoid tissue or at least of a connective tissue quite dense.
Local cholesterosis is a function of the reticulo-endothelial system which enters into the formation of the tumor. Hypercholesterinaemia which is an essential factor in the origin of the xanthoma is without importance in the tumor of giant cells.