Low-grade endometrial stromal sarcoma and undifferentiated endometrial sarcoma: a comparative analysis emphasizing the importance of distinguishing between these two groups.

Endometrial stromal sarcomas (ESSs) are rare tumors whose classification is still controversial. In this study, the authors studied 19 patients diagnosed with ESS at the Hospital S João, Porto, Portugal; reviewed their files and material; and performed immunohistochemical study for CD10, desmin, and smooth muscle actin markers, aiming to compare low-grade endometrial stromal sarcomas (LG-ESSs) and undifferentiated endometrial sarcomas (UESs) using the World Health Organization (WHO) classification. Twelve cases (63%) were classified as LG-ESS and 7 (37%) as UES. The median age at diagnosis was 49 years, and women with LG-ESS tended to be younger than those with UES. Most cases (7/11) had a previous echographic diagnosis of leiomyoma. A biopsy or curettage was performed in 6 cases, providing a definitive diagnosis of malignancy in 4. Frozen section was performed in 4 patients. The majority (63%) of patients were FIGO stage I. Twelve (63%) cases showed diffuse or focal expression of CD10. Desmin and smooth muscle actin expression was focal in 4 (21%) tumors. Patients with LG-ESS had a significant better overall survival than those with UES (P = .026). Mitotic count had no prognostic significance. Our data emphasize the clinical importance of the WHO classification in ESS. It is of utmost importance to establish a proper classification to increase the consistency of data that may be useful for improving clinical and therapeutic management of patients with ESS.