Computed tomography and magnetic resonance imaging characteristics of giant pituitary adenomas

The purpose of this study was to characterize the computed tomography (CT) and magnetic resonance (MR) imaging features of giant pituitary adenoma (GPA) and to demonstrate the pathways of the spread of GPA.

CT and/or MR imaging scans of 356 patients evaluated preoperatively for single pituitary tumor were reviewed. Fourteen tumors (4%) fulfilled the radiologic criteria for GPA. There were 10 male and four female patients, ranging in age from 22 to 71 years (mean, 52 yr). We retrospectively reviewed the CT and MR imaging scans of these patients to characterize tumor appearances and identify the pathways of tumor extension.

Thirteen tumors (93%) extended upward to the suprasellar cistern, and/or hypothalamus and third ventricle. Infrasellar extension through the sellar floor and sphenoid sinus to the skull base, or to the ethmoid sinus or the nasopharynx, was identified in seven patients (50%). Eight patients (57%) had lateral invasion to the cavernous sinus. Temporal and frontal extension was apparent in seven patients (50%) and six patients (43%), respectively. Five patients (36%) had posterior subtentorial extension to the posterior fossa. Histologically, only two GPAs showed invasive features. There was no correlation among histologic features, pituitary hormone concentrations, and evidence of tumor aggressiveness on CT and MRI scans.

GPA has the potential for widespread, multi-directional extension. Our results indicate that any type of pituitary adenoma, regardless of its endocrinologic activity, may invade surrounding structures. Suprasellar invasion is the most common pathway of tumor spread, followed by infrasellar, lateral, anterior, and posterior routes.