Synchronous occurrence of malignant rhabdoid tumor two decades after Wilms' tumor irradiation.

We describe the first case of synchronous malignant rhabdoid tumor arising in the pelvis and the lung two decades after both sites were irradiated for Wilms' tumor. Although the malignant rhabdoid tumor phenotype is controversial as a specific clinicopathological entity, this case exhibited classic clinicopathological features of malignant rhabdoid tumor, including tissue features of a trabecular to alveolar growth pattern; cellular features of characteristic eosinophilic cytoplasmic inclusions exhibiting intermediate filament clusters, large nuclei with prominent central nucleoli, and a dual mesenchymal and epithelial immunocytochemistry profile; and clinical features of a rapidly deteriorating course leading to death 2 months after diagnosis. The occurrence of synchronous malignant rhabdoid tumors in sites irradiated for Wilms' tumor raise interesting questions concerning the relationship of radiation-induced malignancies to putative tumor suppressor gene defects, the distinction of synchronous secondaries from primary recurrences and metastases, and finally the quintessential relationship of malignant rhabdoid tumor to Wilms' tumor.