Neoplasms of endometrial stroma: histopathologic and flow cytometric analysis with clinical correlation.

Ten neoplasms of endometrial stroma (one stromal nodule, four endolymphatic stromal myoses, and five stromal sarcomas) were compared using clinical data as well as histopathologic and flow cytometric parameters. None of the patients with stromal nodules or endolymphatic stromal myosis had extrauterine disease at presentation or tumors displaying a mitotic rate greater than 10/10 hpf (high-power fields), nuclear pleomorphism, atypical mitotic figures, DNA aneuploidy, or a high proliferative index (greater than 10% S phase cells). The stromal nodules were circumscribed and behaved in a benign fashion. The patients with endolymphatic stromal myosis had infiltrative tumors that behaved as low-grade cancers with good responses to therapy. Four of the five patients with stromal sarcoma had extrauterine disease at presentation as well as tumors characterized by a mitotic rate much greater than 10 mitoses/10 hpf, nuclear pleomorphism, atypical mitotic figures, DNA aneuploidy, and a high proliferative index. These four patients had aggressive disease with poor response to therapy. The fifth of the stromal sarcomas had a high mitotic rate, but lacked the other features linked with aggressive behavior; this patient has responded well to treatment. The mitotic count may not be the most useful criterion for predicting biologic behavior in endometrial stromal tumors since it does not always reflect an increased rate of cell turnover as demonstrated by the percentage of cells in the S phase. DNA analysis by flow cytometry yields a more accurate picture of tumor behavior.