Renal angiomyolipoma with sarcomatous transformation and pulmonary metastases

We report the case of a 49-year-old woman with a large renal angiomyolipoma that invaded the liver. In some areas, the tumor had the appearance of a typical angiomyolipoma; however, it also had foci where the spindle cells of the lesion showed marked cytologic atypia and mitotic activity, giving it the appearance of a high-grade sarcoma. Immunohistochemical studies demonstrated expression of vimentin, desmin, and muscle-specific actin by the sarcoma cells; these findings were consistent with leiomyosarcoma. A second, small typical angiomyolipoma was also present in the kidney. In addition, the liver exhibited focal nodular hyperplasia. Three weeks after resection of the primary renal tumor, pulmonary metastases were diagnosed by fine-needle aspiration biopsy. This is the first report of a case of angiomyolipoma with sarcomatous transformation and biopsy-proven metastatic disease.