Surgical cure of hypoglycemia associated with cystosarcoma phyllodes and elevated nonsuppressible insulin-like protein.

A woman with a large, benign cystosarcoma phyllodes of the breast was found to have recurrent, profound hypoglycemia. Plasma levels of nonsuppressible insulin-like protein were increased (15.18 micrograms/ml; normal = 1 to 4 micrograms/ml), whereas levels of insulin and nonsuppressible insulin activity soluble in acid ethanol were normal. Surgical excision of the tumor resulted in immediate and lasting correction of the metabolic abnormalities, although nonsuppressible insulin-like protein levels did not completely return to normal. Surprisingly, preoperative nonsuppressible insulin-like protein levels were highest in blood distant from the tumor site.