Sudden tumour regression with enhanced natural killer cell accumulation in a patient with stage IV breast cancer.

Spontaneous regression of advanced breast cancer is a rare phenomenon. Efforts have been made in order to explain it by means of immunological mechanisms. Corticosteroids have demonstrated important efficacy in the treatment of breast cancer. We present a patient with stage IV breast cancer in whom large tumour masses dramatically regressed during treatment with dexamethasone alone. In this patient, histological and hormonal findings, with results of analyses on surface and intracellular blood cells markers demonstrated significant redistribution of lymphocytes and accumulation of natural killer cells in tumour masses. It seems that dexamethasone has acted through the hypophyse against cancer.