Endometrial stromal sarcoma of the small bowel.

Endometrial stromal sarcoma (ESS) is a rare mesenchymal neoplasm of the uterus, which is predominantly composed of endometrial stromal cells. When this feature is encountered in the extragenital area, the diagnosis is sometimes difficult especially if endometriosis is not present. We report a case of ESS arising in the small bowel without associated endometriosis in a 75-year-old woman and review the literatures for 16 cases of extrauterine extraovarian ESS. The most common site of the extrauterine extraovarian ESS is the gastrointestinal tract (8/16 cases). It is intimately associated with endometriosis (12/16 cases) as the case of ovarian ESS. Most ESSs were immunoreactive for CD10 (5/5 cases), progesterone receptor (10/10 cases), and estrogen receptor (9/11 cases), and negative for CD34 (0/7 cases). It may have a higher tendency for dissemination beyond its site of origin (12/16 cases) than its uterine counterpart. In conclusion, a careful morphological examination combined with immunohistochemical studies and consideration of ESS in the differential diagnosis would help in obtaining an accurate diagnosis in these rare circumstances.