Cellular Leiomyoma versus Endometrial Stromal Sarcoma: A Report of a Rare Case Presenting a Diagnostic Challenge on Intraoperative Frozen Section.

Endometrial stromal sarcomas (ESSs) account for approximately 0.2% of all uterine malignancies. Cellular leiomyoma (CL) often simulates low-grade ESS due to similar cytology. We report the case of a 34-year-old female with a mass per abdomen. Frozen sections showed a tumor with many thin- and thick-walled vessels along with hyaline material. A differential diagnosis of CL and endometrial stromal tumor was suggested. The index case was diagnostically challenging to pathologists. Paraffin sections supplemented by immunohistochemistry (smooth muscle actin, CD10, and beta-catenin) favored CL. Frozen section sometimes leads to over/underestimation of tumor in view of small sampling area of tumor.