EXTRAOSSEOUS PRIMARY AND RECURRENT GIANT-CELL TUMORS - TRANSFORMING GROWTH-FACTOR-BETA-1 AND GROWTH-FACTOR-BETA-2 EXPRESSION MAY EXPLAIN METAPLASTIC BONE-FORMATION

Giant cell tumor (GCT) of bone is a locally aggressive neoplasm with a high incidence of recurrence, usually at the site of previous osseous involvement. Primary and recurrent intraosseous lesions typically are lytic and do not show evidence of tumor-associated osteogenesis. Rare ly, GCT recurs or is primary within soft tissue, and not infrequently, these extraosseous lesions show metaplastic hone formation that is vi sible radiographically. The authors report two recurrent and one prima ry case of extraosseous GCT, all of which exhibited significant deposi ts of metaplastic bone localized to the periphery of the lesions. In s itu hybridization showed messenger RNA (mRNA) for transforming growth factor beta 1 (TGF-beta 1) and transforming growth factor beta 2 (TGF- beta 2) in neoplastic stromal cells and osteoclast-like giant cells wi thin the recurrent and primary extraosseous tumors as well as in activ e osteoblasts on the surfaces of recently formed spicules of metaplast ic bone. In situ hybridization also revealed mRNA for TGF-beta 1 and T GF-beta 2 in primary intraosseous tumors from these cases and from fou r cases in which neither extraosseous recurrence nor osseous metaplasi a was identified. In the microenvironment of the extraosseous soft tis sue, production of these osteoinductive growth factors by GCT may have a paracrine effect on mesenchymal progenitor cells, thereby stimulati ng the osteoblastic differentiation and metaplastic bone formation ass ociated with these lesions. Copyright (C) 1996 by W.B. Saunders Compan y.