Ovarian fibromatous tumours of uncertain biological potential: study of three cases.

Background: The classification of ovarian fibromatous tumours with high mitotic activity is controversial.

Cases Report: The first case was an 18 x 17 x 10 cm left ovarian fibromatous tumour with 17 mitoses/10 HPF detected in a 44-year-old woman. The second case consisted of a 4 x 2.5 x 2 and a 2.5 x 2.5 x 2 cm fibrmatous tumours found, respectively, in the left and right ovaries of a 67-year-old woman. The mitotic count varied from 4 to 6/10 HPF.

Conclusions: Prat & Scully reported that mitotic activity was the most important factor in diagnosing fibrosarcomas, and that cellular pleomorphism was not reliable. Irving et al. suggested that cellular fibromatous neoplasms with bland nuclear features and mitotic count of > or = 4 MFs/10 HPFs should be considered mitotically-active cellular fibromas rather than fibrosarcomas. We propose the term 'fibromatous tumours of uncertain biological potential' when an average mitotic count of 4 or more per 10 HPFs are found and nuclear atypia and necrosis are absent.