INDUCTION OF RECURRING MYOSITIS-OSSIFICANS BY INTRATHYMIC INJECTION OF 3-METHYLCHOLANTHRENE-TREATED CELLS IN RATS

Studies were performed to ascertain the effects of transplantation of thymic cells exposed in vivo to 3-methylcholanthrene (3-MC) on the ind uction of malignancies in Copenhagen rats. Three recipient rats unexpe ctedly developed tumors which bore histological resemblance to myositi s ossificans of humans. Specifically, histology revealed areas of peri pheral ossification with the appearance of zones of primitive osteoid with a central cellular area. Other areas of the lesions were less wel l organized into characteristic zones or were more or less heterogeneo us. The primary, as well as recurring, lesions appeared in the axilla and were well circumscribed, 24-68 g in weight and 2-7 cm in diameter. Flow cytometric analyses of DNA content indicated that these tumors c ontained cells with abnormal DNA characteristics as well as proliferat ing cells. Coupled with the observation that after excision these tumo rs recurred, the data suggest that these myositis ossificans lesions w ere malignancies. (C) 1994 Academic Press, Inc.