Transition from low-grade endometrial stromal sarcoma to high-grade endometrial stromal sarcoma.

We report on a case of a primary low-grade endometrial stromal sarcoma (ESS) that progressed to a secondary high-grade ESS. In the secondary tumor, the immunohistochemical profile and focal tumor cell proliferation pattern suggested that this tumor was not truly undifferentiated, but possessed features of endometrial stroma. Low-grade ESS of our patient's primary tumor showed p53 protein overexpression, which is unusual in low-grade ESS, and her secondary high-grade ESS showed more prominent p53 immunoreactivity. This indicates that low-grade ESS that shows p53 immunoreactivity might progress to high-grade ESS, and it is considered that such cases of low-grade ESS should pay attention to the prognosis. Immunoreactivity for epidermal growth factor receptor was observed in both tumors, suggesting a relationship between the primary and secondary tumors in our case. Further study requires more immunohistochemical data for cases in which low-grade ESS transitions to high-grade ESS; in particular, data on epidermal growth factor receptor expression are necessary to define new therapeutic strategies for ESS.