Pituitary adenomas and granular cell tumors. Incidence, cell type, and location of tumor in 100 pituitary glands at autopsy.

Incidentally detected pituitary adenomas were investigated in 100 pituitary glands at autopsy to determine the number, cell type, and location of tumors, and the presence of coexisting granular cell tumors in the neurohypophysis. Pituitary glands were sagittally sectioned at 1.5-mm intervals in toto and embedded in 1 cassette to orient location of each tumor. Twenty-four pituitary glands harbored adenomas, most smaller than 3 mm and the largest 6 x 5 x 4 mm. Two pituitary glands contained double adenomas of immunocytochemically different cell types. Of the 26 adenomas, 10 had lactotrophs, 2 had mixed lactotrophs-somatotrophs, 1 had mixed lactotrophs-luteinizing hormone cells, and 12 were nonfunctioning. One adenoma with adenocorticotropic hormone cells was also detected. Thus 25 of 26 (96%) adenomas were either lactotrophic or nonfunctioning; this percentage is much higher than that of surgically resected tumors. Twenty-two tumors were contiguous with or adjacent to the capsule from which the adenomas originated. Nine granular cell tumors were noted in the neurohypophysis; 3 coexisted with pituitary adenomas. Fourteen additional cases revealed small granular cell nests. Thus the incidental finding of nonfunctioning pituitary adenomas is relatively common in adults (24% of cases in this study), and the coexistence of pituitary adenomas and granular cell tumors may suggest a possible histogenic connection between anterior and posterior pituitary tumorigenesis.