Parovarian fibroma with heterotopic bone formation of probable wolffian origin

Parovarian neoplasms of wolffian duct origin are very unusual. This article presents the first report of a case of parovarian fibroma with heterotopic bone formation of probable wolffian duct origin. The tumor cells present among mature collagen bundles were fibroblast-like cells, while those at the sites of cellular proliferation were either undifferentiated mesenchymal cells or had differentiated into osteoblasts. In the bone matrix, the tumor cells had differentiated into osteoblasts and connective tissue had ossified.