Brain metastasis from thymic carcinoma in association with SIADH and pituitary enlargement: a case report.

A 49-year-old white female presented to the emergency room complaining of severe headaches. A brain computed tomography (CT) showed a large right temporal mass that measured 2.9 x 5 cm. Sodium was low at admission, which indicated syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Her pituitary gland was enlarged. Thorax CT revealed a large anterior mediastinal mass measuring 6.3 x 3.6 cm. Pathology revealed a poorly differentiated carcinoma arising from the thymus. This case is unique because thymic cancer rarely results in brain metastases and very rarely causes SIADH with changes in pituitary volume and signal quality.