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, alpha-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.