Hepatocellular carcinoma as second malignant neoplasms in successfully treated Wilms' tumor patients. A National Wilms' Tumor Study report. Although rare, second malignant neoplasms (SMN) after treatment for Wilms' tumor are deadly. A recent National Wilms' Tumor Study (NWTS) report identified 15 patients with second malignancies discovered over 14,381 person-years of observation. This report described four patients with secondary hepatocellular carcinoma in greater detail. These patients were strikingly similar in that all had right-sided tumors and each one had received right upper-quadrant irradiation. All patients died shortly after diagnosis of the SMN. 