Abstract: Objective To investigate the pathogenesis, clinicopathological characteristics, diagnosis, differential diagnosis and prognosis of endometrioid stromal sarcoma of the ovary.Methods One case of endometrioid stromal sarcoma of the ovary was studied with HE and immunohistochemical Envision staining.The related literatures were reviewed.Results The tumor’s histological and immunophenotype were similar to those of endometrial stromal sarcoma of the uterus.The tumor was composed of short spindle cells resembling those of proliferative endometrial stroma.Small vessels resembling endometrial spiral arteriole, which were surrounded by whirlpool-form tumor cells, were easily found.The tumor cells were positive for vimentin and CD10, and negative for Calretinin, α-inhibin, H-caldesmon, CD99, CD117, CD34, desmin, SMA and CK(AE1/AE3).Conclusion Endometrioid stromal sarcoma of the ovary is a clinically indolent malignant tumor which is extremely rare.Its main differential diagnosis should include invasion or metastasis of endometrial stromal sarcoma and thecofibroma.

Key words: Ovary:Endometrioid stromal sarcoma, Immunohistochemistry