Malignant fibrous histiocytoma in rats at sites of implanted millipore filters.

Soft-tissue tumors developing in rats at the site of implanted Millipore filters showed the structural, cytochemical, and biologic characteristics of the malignant fibrous histiocytomas occurring in man. Evidence from this tumor model suggests that malignant fibrous histiocytomas can arise from pluripotential mesenchymal stem cells which are not derived from the mononuclear/phagocytic system and that chronic inflammation and scarring may predispose to their development.