ScholarWorks@경상국립대학교

초록

Uterine angiomyolipoma (AML) is an exceptionally rare mesenchymal tumor of the perivascular epithelioid cell tumor (PEComa) family. Most cases are benign and exhibit a triphasic histologic pattern. Although extragenital PEComas typically show strong, diffuse HMB-45 reactivity, uterine AMLs/PEComas often exhibit weak or negative staining, thereby introducing diagnostic uncertainty. We describe a rare case of uterine AML with diffuse nuclear atypia in a postmenopausal woman, which mimicked a degenerative leiomyoma or leiomyosarcoma. A 49-year-old postmenopausal woman presented with the rapid enlargement of a uterine mass that had been followed for four years as a presumed leiomyoma. Imaging revealed a well-circumscribed uterine mass with heterogeneous enhancement, cystic degeneration, and restricted diffusion on MRI. A total hysterectomy was performed. Grossly, the tumor measured 8 cm. Microscopically, it consisted of pleomorphic epithelioid cells (70%), mature adipose tissue (20%), and thick-walled vessels. Immunohistochemistry revealed diffuse smooth muscle actin (SMA) positivity, while Human Melanoma Black (HMB)-45 and Melan-A were negative. Only one mitosis per 50 HPF was identified, with no atypical mitoses or necrosis, and the Ki-67 index was low (<5%). The patient has remained disease-free for 56 months post-surgery. This case represents the first documented HMB-45-negative uterine angiomyolipoma with diffuse nuclear atypia, characterized by a low mitotic index, low Ki-67 proliferation rate, and a benign 56-month follow-up. It broadens the morphologic spectrum of uterine AML, demonstrating that diffuse nuclear atypia can occur in HMB-45-negative tumors with benign behavior, and that atypia alone should not be interpreted as evidence of malignancy. Recognition of this rare variant is essential to avoid misdiagnosing it as leiomyosarcoma.

키워드