Germline mutations in the tricarboxylic acid (TCA) cycle enzyme fumarate hydratase (FH, EC 4.2.1.2) lead to hereditary leiomyomatosis and renal cell cancer (HLRCC, OMIM #150800), a genetic cancer syndrome characterized by benign smooth muscle tumors, uterine fibroids, and a highly malignant form of papillary and collecting duct renal cell cancer. Here, FH is linked to benign smooth muscle neoplasm.