Colorectal adenocarcinoma as a second malignant neoplasm following Wilms' tumor and rhabdomyosarcoma.

Colorectal carcinoma is one of the most common primary malignancies in adults and occurs in older patients after pelvic radiation. It is rare in children and young adults. We report two cases of colonic adenocarcinoma which were second malignant neoplasms following treatment for early childhood malignancies. One child had Wilms' tumor at 9 months of age treated with preoperative radiation and surgery. He developed radiation colitis and multifocal intestinal adenocarcinomas 42 years later and died with abdominal carcinomatosis. The second child had retroperitoneal embryonal rhabdomyosarcoma at age 1 year and was treated with preoperative radiation, surgery, and chemotherapy. At age 2 years he had radiation colitis; at age 11 years he had rectal adenocarcinoma associated with adenomatous polyps, focal adenomatous change and radiation colitis. Immunohistochemical studies revealed p53 positivity in both adenocarcinomas and in adenomas from the second patient, suggesting that p53 mutation was involved in carcinogenesis. The history of high-dose radiation in early childhood and the multifocal lesions suggest the adenocarcinomas in both patients were second malignant neoplasms, with associated reactive and benign neoplastic and premalignant lesions well documented in one case. These two cases document the phenomenon of early onset of adult type tumors in survivors of childhood cancer and emphasize the need for continued clinical evaluation of patients at risk for second malignant neoplasms.