A case of extrauterine low-grade endometrial stromal sarcoma

Background: Extrauterine low-grade endometrial stromal sarcoma is extremely rare and has not, to our knowledge, been cytologically reported in Japan. Cases: A-45-year-old Gravida 2, para 1, woman unsuccessfully for treated endometriosis was found to have soft yellowish white tumors 8 cm and 4.5 cm in diameter, in both periovaries. Tumors were composed chiefly of stromal cells histologically resembling endometrial stroma. Imprint cytology showed isolated and focally clustered cells. Tumor cells had oval nuclei and scant cytoplasm. Nuclei had fine chromatin and nucleoli were not visible. Nuclear atypia was mild and mitotic figures were not found. Immunocytochemically, tumor cells were positive estrogen and progesterone receptor. Conclusion: It was difficult to diagnose this case by cytology alone, but imprint cytology in conjunction of histology and observing tumor cells were important in definitive diagnosis. If small round cells of idiopathic origins are found, immunohistochemical staining of hormone receptors is useful in diagnosis.