ULTRASTRUCTURAL-STUDY OF A PITUITARY-ADENOMA (PROLACTINOMA) WITHIN THE CLIVUS BONE USING IMMUNOELECTRON MICROSCOPY

In a case of a pituitary adenoma in the clivus bone in a 71-year-old m an, ultrastructural investigation using conventional aldehyde-fixed, e poxyembedded tissue revealed the tumor to be composed of cells with eu chromatic nuclei, dense nucleoli, abundant rough endoplasmic reticulum , spherical secretory granules, and granule extrusion at the lateral c ell surface, all of which suggest a prolactin-producing adenoma. Using a protein A-gold immunolabeling technique on snap-frozen tissue subse quently fixed in a mild fixative and embedded in a hydrophilic resin, the presence of prolactin immunoreactivity within secretory granules a t the ultrastructural level was demonstrated. This case represented th e first use of protein A-gold immunolabeling at the electron microscop ic level for diagnostic purposes at our institution and exemplifies th e value of this technique when the need for diagnostic immunoelectron microscopy is not anticipated. Because this tumor arose in an unusual location, ultrastructural study, including immunoelectron microscopy, not only confirmed the light microscopic diagnosis of pituitary adenom a, but further allowed subclassification of the tumor.