Expanding the spectrum of AFF2 undifferentiated sarcoma associated to endometriosis: a novel ZDHHC9::AFF2 fusion sarcoma with high-grade features and poor prognosis
The AFF2 gene encodes a protein involved in transcriptional regulation and chromatin remodeling. While primarily associated with Fragile X syndrome, AFF2 fusions have recently been identified in certain malignancies, mostly sinonasal squamous cell carcinoma. Recently it has been implicated in an intra-abdominal sarcoma linked to endometriosis. We present the case of a 71-year-old woman with a 19 cm ovarian mass arising in cystic endometriosis. Histological examination revealed high-grade undifferentiated sarcoma with spindle to epithelioid morphology, high nuclear atypia, a high mitotic index, and extensive necrosis. Immunohistochemistry demonstrated positivity for Vimentin, ER, PR, CD10, focal WT1, Desmin, and NTRK, with aberrant