The gonadotroph origin of null cell adenomas

The term "null cell" adenoma was first proposed in 1980 to designate pituitary adenomas lacking clinical, biochemical and morphological markers to disclose their cell origin.

The aim of this study was to investigate the presence of α- and β-gonadotropin subunits in clinically nonfunctioning pituitary tumors, which were initially immunonegative and thus diagnosed as null cell adenomas. For this reason, we reapplied immunohistochemistry using a more sensitive method comprising a tyramide signal amplification technique, combined with a polymer antibody immunohistochemical detection system.

With this approach, all these previously negative tumors became positive for α- and β-gonadotropin hormone subunits.

Our results prove that so-called "null cell" adenomas produce α-SU or/and β-FSH or β-LH and therefore are gonadotrph adenomas in origin.