Highly Invasive and Metastatic High-grade Endometrial Stromal Sarcoma With BCOR Gene Alterations: A Case Report

Background: The coexistence of a uterine leiomyosarcoma and a high-grade endometrial stromal sarcoma (HGESS) is extremely rare, especially when one of the components causes metastasis. Case Report: A 46-year old female with aggravated abdominal pain for more than 4 months was diagnosed with uterine malignant mesenchymal tumor composed of predominantly a leiomyosarcoma (99%) and a minor component of HGESS with BCL6 corepressor (BCOR) gene alterations (1%), with ovarian and pelvic metastases. Results: The volume of HGESS with BCOR gene alterations accounted for less than 1% of the tumor mass but caused ovarian and pelvic metastases. Conclusion: HGESS with BCOR gene alterations is extremely aggressive. We suggest that when both components of HGESS with BCOR gene alterations and uterine leiomyosarcoma are present in one patient, the HGESS with BCOR gene alterations needs to be highlighted in the pathological report, even if it accounts for less than 1% of the tumor volume.