Low grade endometrial stromal sarcoma (LG-ESS) is a rare malignancy of mesenchymal origin in the female reproductive system, which has the characteristic of late recurrence. Endometrial carcinoma is a group of epithelial tumors, and is one of the most common gynecological malignancies among women worldwide. The coexistence of LG-ESS and endometrial carcinoma is extremely rare, and there is no relevant report about the collision of endometrial carcinoma and recurrent LG-ESS currently. In the present study, we report a tumor of recurrent LG-ESS accompanied with endometrioid adenocarcinoma in a young patient 8 years after hysterectomy. She was first diagnosed with LG-ESS at the age of 19 and received fertility-sparing therapy. During the 13-year follow-up period, she successfully delivered and experienced two recurrences of LG-ESS, and an unexpected endometrioid adenocarcinoma component was found in the second recurrent tumor. Adjuvant chemotherapy and endocrine therapy were administrated to the patient after completely removing the tumor, and no sign of disease recurrence or metastasis were found 7 months after the last surgery. This study emphasizes the importance of long-term management of LG-ESS and brings new insights to clinicians and pathologists about collision tumors involving recurrent tumor.
Keywords: collision tumor; endometrioid adenocarcinoma; hysterectomy; recurrent low grade endometrial stromal sarcoma.