Severe lymphocytic adenohypophysitis with selective disappearance of prolactin cells: a histologic, ultrastructural and immunoelectron microscopic study.

We report the first documented example (case 1) of lymphocytic adenohypophysitis (LAH) associated with selective destruction of prolactin cells. The morphologic data are compared to those obtained in another, more typical case (case 2). Case 1 was a 35-year-old woman with remote history of pregnancy who presented with headache, oligomenorrhea and visual disturbances. The blood prolactin level was nearly undetectable, but no deficiency of other pituitary hormones was evident. A sellar and parasellar mass compressing the optic chiasm was removed transsphenoidally. Histology demonstrated massive infiltration with lymphocytes, plasma cells and macrophages causing marked destruction of pituitary acini. Part of the gland was fibrotic. Immunocytochemistry documented all pituitary hormones, but only few cells, probably mammosomatotrophs, were immunoreactive for prolactin. Electron microscopy and immunoelectron microscopy using double gold labeling for growth hormone and prolactin detected no prolactin cells. A striking ultrastructural finding was the prominence of folliculostellate cells in areas of active cell destruction supporting the presumed immune role of these cells. LAH in case 2 (24-year-old woman) became manifest during late pregnancy, causing pituitary enlargement and visual field defects. Pituitary tests showed no major hormonal deficits. Moderate hyperprolactinemia was appropriate for her pregnancy status. A sellar mass, thought to be adenoma, was removed. Histology demonstrated multifocal LAH without major destruction of acinar structures. Immunocytochemistry and electron microscopy documented all pituitary cell types including the marked abundance of prolactin-producing cells, resultant of gestational prolactin cell hyperplasia. In addition to prolactin cells and growth hormone cells, immunoelectron microscopy showed several bihormonal mammosomatotrophs, also appropriate for pregnancy.