Anatomical Pathology Interesting Case Conference

Discussion:

Leiomyosarcoma is a rare, aggressive malignant neoplasm that originates from smooth muscle cells. Although it may occur in the perirenal space, it most commonly arises from the retroperitoneal vasculature, such as the renal vein or the inferior vena cava, or from the smooth muscle of the renal pelvis.

Patients typically become symptomatic as the tumor enlarges.

Grossly, the tumor appears as a well-circumscribed, gray-white mass. Larger lesions frequently demonstrate areas of hemorrhage, necrosis, and cystic degeneration.

Microscopically, the tumor is composed of short spindle-shaped to oval cells exhibiting marked nuclear pleomorphism, coarse chromatin, and prominent nucleoli. The tumor cells are arranged in intersecting fascicles oriented in parallel and perpendicular planes, as well as in whorled patterns, with areas of increased mitotic activity. Foci of tumor necrosis and hemorrhage may also be present.

Immunohistochemistry shows positivity for SMA, Desmin and Vimentin.

Complete surgical excision with negative margins remains the primary and most effective treatment. Depending on the tumor size, grade, stage, and surgical margin status, adjuvant radiotherapy and/or chemotherapy may be considered to reduce the risk of local recurrence and distant metastasis.