Uterine smooth-muscle tumors with unusual growth patterns include a variety of neoplastic lesions characterized histologically by their similarity to adult smooth muscle tissue. The 3 primary neoplasms are intravenous leiomyomatosis, benign metastasizing leiomyoma, and leiomyomatosis peritonealis disseminata. We present a review of the recent literature along with the clinical and pathologic features of 5 illustrative cases from Mayo Clinic Arizona, Scottsdale.