High-grade endometrial stromal sarcoma with ZC3H7B-BCOR fusion

Abstract

High-grade endometrial stromal sarcoma (HG ESS) is a rare malignant mesenchymal tumour of the uterus which is prone to locoregional recurrence and has a poor prognosis. Recently, distinct molecular genetic subtypes have been described, most notably those harbouring YWHAE-NUTM2A/B fusion, ZC3H7B-BCOR fusion and BCOR internal tandem duplications. We present a case of a 50-year-old woman who initially presented with bowel obstruction and metastatic disease. Her clinical course was characterised by advanced stage and multiple recurrences. Histologically, the tumour showed typical ovoid to spindled cytomorphology with myxoid stroma, relatively uniform nuclear features, and brisk mitotic activity. Immunohistochemistry was negative for CD10, SMA and desmin, but showed strong and diffuse positive labelling with cyclin D1. Next-generation RNA sequencing showed a ZC3H7BBCOR fusion. Awareness of this recently described molecular subcategory of HG ESS and its typical histological features is crucial in separating it from its pathological mimics and in establishing the correct diagnosis.