Leiomyoma with bizarre nuclei occurring post hysterectomy mimicking malignancy: a rare case report

Abstract Introduction/Objective Leiomyoma with bizarre nuclei (LBN), also known as symplastic leiomyoma, represents a rare subtype of benign uterine smooth muscle neoplasm. Histologically, it is characterized by significant cytological atypia in a typical leiomyoma background with rare mitoses and without tumor necrosis. Methods/Case Report We report a case of a 48-year-old woman, status post hysterectomy for symptomatic fibroids, with imaging showing multiple contiguous pelvic masses extending from the pelvis to the upper abdomen and displacing the colon laterally and small bowel posteriorly. The findings were highly suspicious for ovarian malignancy. A bilateral salpingo-oophorectomy and a partial colectomy were performed with tumor debulking and omentectomy. Grossly, multiple well-circumscribed soft masses ranging in size from 1.5-16 cm, in contiguity with pericolonic mesentery with a smooth fleshy cut surface and cystic changes were found. Bilateral ovaries were unremarkable. Microscopically the larger masses were composed of spindle cells with bizarre nuclei throughout, while smaller masses showed foci of bizarrely shaped-spindle cells with bizarre nuclei in a background of a typical leiomyoma. Mono- and multinucleated cells with smudged chromatin were also seen. The mitotic index was low confirmed with a low Ki-67 proliferation index (< 5%). Immunohistochemical stainings showed that the neoplastic cells were positive for desmin, SMA, and caldesmon; and negative for CD10, with a wild type p53 expression. Fumarate hydratase immunostain was retained. MDM2 amplification was not detected by FISH. The morphology and immunohistochemical findings were compatible with LBN. Results (if a Case Study enter NA) NA Conclusion In summary, this is a rare and challenging case of multiple LBN developed years post hysterectomy and clinically mimicking a malignancy.