A difficult to diagnose case of low-grade endometrial stromal sarcoma with smooth muscle differentiation treated with...

Low-grade endometrial stromal sarcoma (LGESS) is a rare uterine tumor, accounting for <1% of all uterine cancer cases. LGESS has several variations and the frequency of tumors exhibiting smooth muscle differentiation is 10-30% of LGESS cases, making such cases even rarer. The present report described the case of a patient with LGESS with smooth muscle differentiation, who was diagnosed as having uterine leiomyoma by preoperative needle biopsy and then underwent laparoscopic surgery. The patient was a 41-year-old woman. MRI findings revealed a diffusely hyperintense uterine tumor on T2-weighted images, thus needle biopsy was performed. This tumor was initially diagnosed as leiomyoma, due to the pathological findings of the biopsied specimen, which possessed tumor cells with spindle-shaped nuclei arranged in a cord and positive immunostaining for smooth muscle actin. The patient was subsequently followed up, and MRI findings after 29 months showed tumor growth. Needle biopsy was performed again and the findings were the same as those of the first biopsy; therefore, this tumor was diagnosed as a leiomyoma and laparoscopic hysterectomy was performed. However, the pathological findings of the excised uterus showed small round tumor cells and CD10 immunostaining positivity, thus the tumor was finally diagnosed as LGESS. The patient requested to be followed up and has shown no signs of recurrence 20 months after surgery. The results of retrospective examination in this case suggested that the presence of regions where only CD10 was positive in immunostaining analysis for SMA and CD10 was useful for needle biopsy diagnosis of LGESS with smooth muscle differentiation.