Pituitary Adenoma with Cholesterol Clefts.

Histologically, cholesterol clefts are often observed in craniopharyngioma, Rathke's cleft cyst, and various granulomas. However, pituitary adenomas with cholesterol clefts are rare. A 46-year-old woman developed visual field disturbance. She had no history of severe headache that would suggest pituitary apoplexy. She presented with homonymous bitemporal hemianopsia and galactorrhea. Blood prolactin level was 63.1 ng/mL Other hypophysial hormone levels were within normal range. Magnetic resonance imaging revealed a pituitary tumor with intratumoral cyst. The cyst showed high intensity on T1- and T2-weighted images. The tumor was demonstrated with iso intensity on T1-weighted image and with high intensity on 12-weighted image. She underwent trans-sphenoidal surgery. The tumor was soft, with yellowish, oily fluid, probably the cyst content. By light microscopy with hematoxylin and eosin staining, a typical chromophobic adenoma of the pituitary was identified. Immunostaining revealed immunoreactivity for ACTH in several cells. Many cholesterol clefts and several hemosiderin pigment containing macrophages were observed. Electron microscopy demonstrated a pituitary adenoma with sparse and small secretory granules and numerous lysosomes. The cyst was most likely caused by focal hemorrhagic infarction, followed by the formation of cholesterol crystals, the appearance of hemosiderin containing macrophages, foreign body product cells, and accumulation of lysosomes.