JAZF1, YWHAE and BCOR gene translocation in primary extrauterine low‐grade and high‐grade endometrial stromal sarcomas

Aims JAZF1 translocation is the most common genetic change in low‐grade (LG) endometrial stromal sarcoma (ESS), and YWHAE and BCOR translocations are common in high‐grade (HG) ESS. Primary extrauterine ESS is rare, and there are limited data on molecular alterations in these tumours. Methods and results Cases of primary extrauterine ESS, comprising eight LG‐ESS cases and five HG‐ESS cases were collected. Haematoxylin and eosin and immunohistochemical staining were used to observe the histomorphology and analyse related protein expression. JAZF1 , YWHAE and BCOR rearrangements were explored with fluorescence in‐situ hybridisation (FISH). In LG‐ESS, the tumour cells resembled normal proliferative‐phase endometrial stromal cells; CD10, oestrogen receptor and progesterone receptor were expressed in all eight cases. In HG‐ESS, the tumour cells had uniform HG round and/or spindle morphology, sometimes with an LG component; CD10 was fully expressed in one case and focally expressed in four cases; BCOR was expressed in all five cases, and cyclin D1 in four of five cases. FISH analysis showed JAZF1 translocation in one of eight LG‐ESS cases (12.5%). YWHAE translocation occurred in four of five HG‐ESS cases, with a positivity rate of 80%. BCOR translocation was absent in all five cases. Conclusions In extrauterine LG‐ESS, the rate of JAZF1 rearrangement was significantly lower than in uterine LG‐ESS. This result limited the value of JAZF1 translocation for diagnosis. YWHAE rearrangement is a common genetic change in extrauterine HG‐ESS. Further studies are required to confirm these findings, especially in LG‐ESS.