Comparison between Immunohistochemical Stains and Serum Hormone Level on Pituitary Adenomas

ABSTRACT

The current classification of pituitary adenomas is based on cell type, largely ascertained by immunohistochemistry and electron microscopy. In an application of immunohistochemistry, pathologists have some problems in judging the results. An immunostaining result does not always correspond with a serum hormone level. It is also difficult to determine the nature of a tumor when a few cells are positive. We performed the immunohistochemical stains on 34 pituitary adenomas using polyclonal antibodies to six pituitary hormones [PRL (prolactin), GH (growth hormone), ACTH (adrenocorticotropic hormone), FSH (follicle-stimulating hormone), LH (luteinizing hormone), TSH (thyroid-stimulating hormone)] and compared with serum hormone level. The serum hormone level was increased in 14 cases (41.2%) of PRL, 7 cases (20.6%) of PRL & GH, 6 pleurihormonal cases (17.6%), 4 nonfunctioning cases (11.8%), 2 cases (5.9%) of FSH, and 1 case (2.9%) of GH. The most common immunohistochemical type of pituitary adenoma was 10 prolactinoma cases (38.5%), followed by 7 pleurihormonal cases (26.9%), 4 null cell cases (15.4%), 3 cases of mixed PRL & GH (11.5%), 1 case of ACTH (3.8%) and 1 FSH & LH case (3.8%). The corresponding rates of the serum hormone level and immunostaining results were 94.1% in GH, 88.9% in TSH, 85.7% in LH, 82.4% in ACTH, 66.7% FSH, and 61.8% in PRL. In the immunostaining for FSH, 12 cases showed less than 5% positivity and most of them exhibited the normal serum hormone level. In conclusion, the most common elevated serum hormone and immunohistochemical type of pituitary adenoma was prolactinoma. The corresponding rate of the serum hormone level and immunostaining result was the highest in GH cell adenoma and was the lowest in prolactinoma. The cells showing less than 5% positivity seem to be entrapped normal cells.