Case series analysis of immunophenotypic evolution during recurrence of low-grade endometrial stromal sarcoma: implications for molecular stability and clinical management

Purpose To investigate the pathological morphology, immunophenotype, and molecular genetic characteristics of recurrent low-grade endometrial stromal sarcoma (LG-ESS) through the analysis of paired primary and recurrent tumor samples. Methods A single-center retrospective analysis was conducted using the clinical data, pathological morphology, immunohistochemical results of estrogen receptor, progesterone receptor (PR), CD10, Ki-67, and fluorescence in situ hybridization findings for JAZF1 and PHF1 gene rearrangements in paired tumor tissues from four patients with LG-ESS. Results Patients’ ages ranged from 22 to 34 years. All cases showed consistent JAZF1 or PHF1 gene rearrangements in both primary and recurrent tumors. However, immunophenotypic alterations were observed during recurrence: one recurrent lesion showed loss of PR expression accompanied by a decreased Ki-67 index, whereas another demonstrated loss of CD10 expression. The median follow-up time was 84 months (range, 36–144 months). The recurrence interval ranged from 3 to 12 years, and all patients remained alive following comprehensive treatment. Conclusion This case series indicates that core driver gene rearrangements remain stable during recurrence in LG-ESS, whereas immunophenotypic evolution may occur in some cases. These preliminary findings suggest that the re-evaluation of biomarkers such as hormone receptors at recurrence may provide valuable guidance for individualized treatment selection (e.g., hormonal therapy). Given the characteristic tendency for late recurrence in LG-ESS, long-term follow-up is essential.