58 cases of Cushing's disease were studied after selective transsphenoidal surgery, by means of histology, immunocytochemistry and morphometry. The qualitative and quantitative results, related to the clinical follow-up of the patients indicated that: 1) when a well-defined tumor was found (62% of the patients), successful outcomes occurred in 88% of the cases, 2) when a tumor could not be found, successful outcomes amounted to only 33% of the cases, a rate that might be related to a surgical exploration of the basophil cell zone "invading" the neural lobe, thus questioning a role of this zone, at least in some Cushing's diseases.