Xanthomatous Hypophysitis: A Novel Entity of Obscure Etiology

We report a case of xanthomatous hypophysitis, a recently described entity of obscure etiology affecting the pituitary gland, in a 43-yr-old women. Histologically it is characterized by infiltration of the anterior pituitary by foamy histiocytes which are strongly immunoreactive for CD68 (histiocytic marker) and are immunonegative for S100 and CD1a. Electron microscopy revealed histiocytes with abundant cytoplasmic lipid droplets and membrane bound vacuoles. Fragments of intact anterior pituitary with preserved vascular and reticulin networks are seen. Xanthomatous hypophysitis resembles neoplasm on clinical and radiologic grounds.