KAT6B and endometrioid stromal sarcoma: In conclusion, the results of our study and previous research suggest that, despite some overlapping morphological and immunohistochemical features with tumors of smooth muscle and endometrial stromal differentiation (LG-ESS and ESN), sarcomas with the KAT6B/A::KANSL1 fusion represent a distinct entity rather than merely a subtype of LG-ESS.