Extrauterine endometrial stromal sarcoma with JAZF1/JJAZ1 fusion confirmed by RT-PCR and interphase FISH presenting as an inguinal tumor

Endometrial stromal sarcomas are rare malignant mesenchymal tumors that usually develop in the uterine corpus and occasionally arise at various extrauterine sites. This report describes the first case of primary extrauterine endometrial stromal sarcoma arising in the extraperitoneal portion of the round ligament presenting as a solitary inguinal mass in a 46-year-old woman. The patient presented gradually growing tumor in the right inguinal region. Local tumor resection was performed and no recurrence or metastasis was found at 15 months after the operation. Histological examination revealed that the tumor comprised uniform, spindle-shaped cells with blunt nuclear figure and scattered small arteries, and infiltrated into adjacent tissue. No endometriosis was morphologically identified in the lesion. Immunohistochemically, the tumor cells were positive for CD10, estrogen receptor, progesterone receptor, α-smooth muscle actin, and calponin. We confirmed JAZF1/JJAZ1 fusion by reverse transcription–polymerase chain reaction and the corresponding chromosomal translocation by interphase fluorescence in situ hybridization on paraffin sections. It is essential that the inguinal region should be recognized as a possible primary site of endometrial stromal sarcoma, and the detection of a JAZF1/JJAZ1 fusion can be useful when the diagnosis is not confirmed by microscopic observation or immunohistochemistry for the tumor arising in extrauterine sites.