Development of syndrome of inappropriate secretion of antidiuretic hormone during progression of metastatic breast cancer.

A patient who developed syndrome of inappropriate secretion of antidiuretic hormone (SIADH) during progression of metastatic breast cancer is described. The classic criteria for SIADH as defined by Bartter and Schwartz were fulfilled and conditions other than malignant disease were excluded as causes of the syndrome. To the knowledge of the authors SIADH has never been reported to develop during the course of malignant disease in a patient with metastatic breast cancer. It should be borne in mind that SIADH may occur in patients with malignant disease and hyponatraemia, even in the absence of small-cell lung cancer, which is the classic tumour type to develop SIADH.