A 41-yr-old lady with abnormal uterine bleeding underwent total abdominal hysterectomy. Histologic assessment revealed an endometrial stromal sarcoma (ESS) with minimal cytologic atypia and low mitotic count (up to 7/10 high-power fields) with only focal myxoid areas, morphologically corresponding to a low-grade ESS. Immunohistochemical stains showed cyclin D1 and CD10 positivity, and negative staining for CD117 and progesterone receptor. This tumor was clinically aggressive and recurred 6 mo later. The patient died 19 mo following initial diagnosis. Molecular analysis revealed a ZC3H7B(exon 10)-BCOR (exon 7) gene fusion. Subsequent BCOR immunohistochemistry was weakly positive. ESS with ZC3H7B-BCOR gene fusion is classified as a low-grade ESS in some classification schemes, and is also characterized as being typically myxoid. This report supports emerging evidence that ESS with ZC3H7B-BCOR gene fusion may have an aggressive clinical course in spite of its low-grade histology. This report further expands the morphologic spectrum of ZC3H7B-BCOR fusion ESS to include nonmyxoid histology. Finally, this report underlines the value of molecular analysis in the proper classification of this aggressive tumor with deceptive low-grade histology.
Department of Pathology and Laboratory Medicine (S.M., C.H.K., A.P.C.W., S.K.L.-T., K.T.E.C.)
Department of Gynaecological Oncology (S.L.L., T.Y.K.L.), KK Women’s and Children’s Hospital
Division of Medical Oncology, National Cancer Centre (R.Q.), Singapore, Singapore
The authors declare no conflict of interest.
Address correspondence and reprint requests to Sorsiah Mansor, MBBch, BAO, FRCPath, Department of Laboratory Medicine, KK Women’s and Children’s Hospital, 100 Bukit Timah Road, Singapore 229899, Singapore. E-mail: email@example.com.