Wilms' tumor presenting as sudden death due to tumor embolism.

The clinical and pathologic features of two unusual cases of Wilms' tumor are described. Both cases presented as sudden death due to tumor embolus. One patient, a 7-year-old girl, had a massive tumor embolus filling the right main pulmonary artery. The second patient, a 6-year-old boy, had pulmonary artery tumor embolus, widespread metastases to lungs, lymph nodes, mesentery, bowel, brain, and nerves, and tumor emboli in the myocardial and epicardial vessels and carotid artery. The renal vein was invaded in both patients. The histologic characteristics of the two tumors was strikingly similar, both showing a blastemal predominant pattern with minimal epithelial differentiation in the form of tubules. Anaplasia was not a feature. To our knowledge, the initial presentation of Wilms' tumor as sudden and unexpected death has not been previously described.