Bizarre But Benign: A Case Report of an EHHADH::RAD51B Rearranged Endometrial Polyp With Bizarre Stromal Cells.

Endometrial polyps with bizarre stromal cells are a rare histological variant of endometrial polyps characterized by striking nuclear atypia that can mimic features of malignant mesenchymal neoplasms, particularly Müllerian adenosarcoma (MA). Despite their alarming cytological appearance, these lesions typically follow a benign clinical course, making an accurate diagnosis essential to avoid unnecessary aggressive surgical interventions. Here, we present the case of a 53-yr-old woman with a 3-mo history of postmenopausal bleeding. Imaging revealed an 18 mm endometrial lesion with circumferential Doppler flow. Subsequent hysteroscopic resection and histopathological examination identified an endometrial polyp containing atypical, enlarged, and hyperchromatic stromal spindle cells with characteristic "smudged" chromatin. Mitotic activity was negligible, and there was no evidence of the leaf-like architecture or periglandular cuffing typical of MA. Immunohistochemical profiling showed diffuse positivity for CD10 and HMGA2, p53 wild-type expression, and a low Ki-67 proliferation index (<5%). Molecular analysis via FusionPlex Next Generation Sequencing revealed an EHHADH::RAD51B fusion, a novel gene fusion that expands the limited body of molecular data on endometrial polyps with bizarre stromal cells.