Squamous-cell nests in the pars tuberalis of the human pituitary: Immunocytochemical and in situ hybridization studies.

Abstract

Twenty-one autopsy-obtained human pituitaries were studied by histology, immunocytochemistry, and in situ hybridization to elucidate the characteristics of squamous-cell nests in the pars tuberaiis. Histologically, squamous-cell nests were composed of aggregates of squamous epithelial cells or squamous epithelial cells and adenohypophysial cells, which were immunoreactive mainly for FSH, LH, and the α-subunit (less frequently for ACTH). A gradual transition was seen from adenohypophysial cells to squamous cells at the periphery of several squamous-cell nests. Squamous-cell nests were immunoreactive for cytokeratin and EMA but were immunonegative for vimentin, demin, GFAP, S-100 protein, synaptophysin, chromogranin, and estrogen receptor. In situ hybridization revealed ER receptor mRNAs in both squamous-cell nests and adenohypophysial cells, but GH PRL, and POMC mRNAs could not be demonstrated in squamous-cell nests, and α-subunit mRNA was found only in 2 of 11 samples. Our results indicate that squamous-cell nests in the pars tuberalis derive by metaplasia from adenohypophysial cells rather than from remnants of the Rathke's pouch.Endocr Patho! 4:155-161,1993.