Use of immunohistochemical and morphologic methods for the identification of human growth hormone-producing pituitary adenomas

Indirect immunoperoxidase and immunofluorescent techniques were used for the detection of growth hormone in routinely processed human pituitary adenomas. With the immunoperoxidase method, distinct immunoreactive cells could be demonstrated in 15 adenomas; all except for one were associated with acromegaly. Immunofluorescence was less useful because of autofluorescence due to the fixation. In histologic stainings, the immunoreactive cells were acidophyl. With immunohistochemistry and electron microscopy, densely granulated and sparsely granulated adenomas could be distinguished. Sparse granulation was associated with an expanded rough-surfaced endoplasmic reticulum and Golgi complex. Clinically, the sparsely granulated adenomas were characterized both by active hormone secretion and aggressive local growth. It is concluded that the immunoperosidase method is of value for functional classification of pituitary adenomas. For information about secretory activity we suggest that electron micrographs of adenoma cells be examined.