Molecular characterization of a population-based series of endometrial stromal sarcomas in Kuwait

Endometrial stromal sarcomas (ESSs) frequently harbor genetic fusions, including JAZF1-SUZ12 and equivalent fusions in low-grade ESS (LGESS) and YWHAE-NUTM2 in high-grade ESS (HGESS). This study aims to classify a population-based series of ESSs in Kuwait based on the 2014 World Health Organization classification system and to assess the diagnostic use of interferon-induced transmembrane protein 1 (IFITM1) immunomarker for ESSs. Twenty ESSs including 19 LGESSs and 1 HGESS treated during the period between 2002 and 2013 were identified, and the cases were reviewed and characterized using fluorescence in situ hybridization and immunohistochemical studies. Thirteen (81.3%) of 16 LGESSs with interpretable results showed JAZF1 and/or PHF1 genetic rearrangements by fluorescence in situ hybridization, and the only HGESS in the series showed YWHAE genetic rearrangement. All LGESSs with interpretable results showed positive immunostaining for CD10 compared with 11 (61%) of 18 that showed positive immunostaining for IFITM1; 4 of 7 IFITM1-negative LGESSs showed JAZF1 and/or PHF1 rearrangements. A series of uterine leiomyomas, leiomyosarcomas, adenosarcomas, and carcinosarcomas were included for comparison, and positive IFITM1 staining was found in 1 of 10 leiomyomas, 3 of 13 leiomyosarcomas, 3 of 4 adenosarcomas, and 3 of 8 carcinosarcomas, compared to 0 of 10 leiomyomas, 9 of 13 leiomyosarcomas, 3 of 4 adenosarcomas, and 5 of 8 carcinosarcomas that were positive for CD10. Our results demonstrated characteristic genetic rearrangements in a high percentage of LGESSs in this Middle Eastern population, and IFITM1 antibody appears to be less sensitive than CD10 for LGESS.