OBJECTIVETo investigate the clinicopathologic features and the prognostic factors of endometrial stromal sarcoma (ESS).

METHODS55 cases of endometrial stromal sarcoma were reviewed and categorized into 3 pathologic types based on the related literatures, i.e., low grade endometrial stromal sarcoma (LGESS), undifferentiated endometrial sarcoma with nuclear uniformity (UES-U) and undifferentiated endometrial sarcoma with nuclear pleomorphism (UES-P). Meanwhile, the pathologic features were reviewed, including fibroid, myoid, mucoid, and epithelioid differentiation and mitotic index. Clinical and follow-up data were collected.

RESULTSIn endometrial stromal sarcoma, two or three pathologic types co-existed in one case, including 12.8% (5/39) of LGESS, 5/9 of UES-U, and 5/7 of UES-P. Mitotic index varied in different regions of one tumor from rare to high. Multi-differentiation was also commonly seen in ESS. The numbers of cases in LGESS, UES-U and UES-P were 39, 9 and 7, with recurrence rate of 51.6% (16/31), 5/6 and 2/3, respectively. There was no death case in LGESS, and 2 cases were died in UES-U and UES-P, respectively. In the 2 death cases of UES-U, both had focus of UES-P. There was a significant difference in the recurrence rate between cases with different mitotic index (≥ 10/10 HPF and < 10/10 HPF, P = 0.009), especially in LGESS group. All death cases had high mitotic index (> 30/10 HPF).

CONCLUSIONSIt is a common phenomenon in ESS that two or three pathologic types may exist in one case, especially in UES-U and UES-P. And multi-differentiation is also commonly seen in ESS. So adequate pathologic sampling is important for pathologists to make a correct diagnosis of ESS in daily work. The recurrence rates are significantly higher in cases with high mitotic index, especially in LGESS. In addition, the presence of UES-P and high mitotic index may increase the risk of death in the patients.