Hypercalcemia associated with immunoreactive parathyroid hormone in a malignant rhabdoid tumor of the kidney (rhabdoid Wilms' tumor).

Severe hypercalcemia occurred in a child with metastatic disease from a rhabdoid tumor of the kidney. Because there was no evidence of skeletal involvement by tumor, an investigation of the cause for hypercalcemia was undertaken. A greatly elevated serum concentration of immunoreactive parathyroid hormone (iPTH) was documented. This together with the observation of histologically normal parathyroid glands and the immunohistologic demonstration of parathyroid hormone within tumor cells supports the hypothesis of ectopic iPTH production by the tumor. The concurrence of an unusual metabolic complication with an infrequently encountered tumor variant is notable.