Mixed low grade and high grade endometrial stromal sarcoma of uterus: differences on immunohistochemistry and chromosome in situ hybridisation.

A case of a 64 year old woman with a tumour of the uterus is reported. The patient presented with postmenopausal bleeding and subsequently underwent total hysterectomy and bilateral salpingo-oophorectomy. Sections of the tumour showed a low grade endometrial stromal sarcoma coexisting with areas consistent with high grade sarcoma. The sarcoma cells, in both the low and high grade areas, were positive for vimentin and negative for desmin and cytokeratin on immunohistochemistry. While the sarcoma cells in the low grade region showed immunoreactivity for oestrogen and progestogen receptors, those in the high grade region did not. Using chromosome in situ hybridisation, the low grade portion of the sarcoma was diploid for chromosomes X, 11, 12, and 17, whereas the more anaplastic areas were aneuploid for these chromosomes. This case may represent an example of high grade endometrial stromal sarcoma arising by dedifferentiation from a low grade stromal sarcoma. Adequate sampling is important in identifying such anaplastic changes as the origin of the tumour will affect patient management.