Myxoid endometrial stromal sarcoma: report of two cases with emphasis on its diagnostic problems

Aims: To address the diagnostic problems of uterine myxoid endometrial stromal tumor.

Methods: We investigated the clinicopathologic and immunohistochemical features of 2 myxoid endometrial stromal sarcomas.

Results: Patient 1 had a recurrent pelvic tumor. She had a history of abdominal hysterectomy for "uterine multiple leiomyomas" 3 years ago. The pelvic tumor and her previous uterine tumor were both composed of myofibroblast-like spindle cells, and small oval cells in a myxoid matrix. The mitotic figures were up to 3-4/10 HPFs. There were numerous small thin-walled vessels and anastomosing capillaries. Patient 2 had a gelatinous polypoid mass in the uterine cavity. The tumor harbored plump spindle tumor cells loosely embedded in the prominent myxoid matrix. It morphologically mimicked an inflammatory myofibroblastic tumor. However, it had a tongue-like myometrial invasion and vascular involvement. By immunohistochemistry, the tumor cells in both cases were all positive for CD10, and negative for caldesmon, CD117, CD34 and ALK.

Conclusions: Endometrial stromal tumors can show a substantial myxoid component. Careful morphologic assessment and immunohistochemical study will contribute to their distinction from myxoid leiomyosarcoma, inflammatory myofibroblastic tumor and other morphologic mimickers.