Extrarenal teratoid Wilms' tumor: two cases in unusual locations, one associated with elevated serum AFP.

Teratoid Wilms' tumor is an unusual morphological entity characterized by a classic triphasic malignancy with predominantly heterologous tissue. The authors describe two cases of teratoid Wilms' tumor with an extrarenal site: one in a 13-year-old girl with vaginal spotting (patient 1) and another in a 1-day-old girl with a sacrococcygeal mass (patient 2). The tumors were located in the vagina and coccyx, respectively. Under the initial clinical diagnosis of sarcoma botryoides in patient 1 and teratoma in patient 2, the masses were removed. Microscopically, both tumors were composed of typical triphasic Wilms' tumor tissue with primitive cartilage and skeletal muscle, and squamous and columnar mucinous epithelia. The patient with sacrococcygeal mass (patient 2) had an elevated serum AFP level. The patients were given chemotherapy and have now remained disease free for 7 years 1 month, and 2 years 5 months after surgery, respectively. Familiarity with this rare variant of Wilms' tumor might be important in arriving at a correct diagnosis.