Tomographic abnormalities simulating pituitary microadenomas.

False-positive and false-negative interpretations of sellar tomography were found in about one-fifth of cases in a recent autopsy study correlating the presence of pituitary microadenomas with abnormal sellar tomograms. An analysis of minor variations in the bony configuration of the sella disclosed variations due to posterior lobe asymmetry, intercavernous venous channels, bony asymmetry, and an empty sella in 27 of the 120 sellas examined. In some instances, the asymmetry resulted from a combination of these causes. A further study of 50 pituitary glands in situ showed posterior lobe asymmetry to be a common anomaly (76%) that can produce an obvious disparity between the two halves of the sella. Thus, the minor radiologic criteria of local thinning of the anterior wall or floor, slant of the floor, or asymmetry of the two halves of the sella must be interpreted with caution as being indicative of the presence of pituitary microadenoma. In the absence of clinical or biochemical dysfunction, the changes more likely result from explainable anatomic causes.