Comparison of growth hormone-producing and non-growth hormone-producing pituitary adenomas: imaging characteristics and pathologic correlation.

PURPOSE: To identify characteristic features of growth hormone (GH)-producing pituitary adenomas.

MATERIALS AND METHODS: A total of 174 pathologically proven pituitary adenomas were evaluated retrospectively on magnetic resonance (MR) images to determine the signal intensity (on T2-weighted images), maximum diameter, and amount of suprasellar and infrasellar extension. For microadenomas, sellar depth was also measured. GH-producing adenomas were classified at histologic evaluation as densely or sparsely granulated. Specimens from 38 adenomas were stained to assess the amounts of fibrous tissue, iron, and amyloid they contained. Results were correlated with the size and hormonal activity of adenomas by using the chi2, unpaired t, and Mann-Whitney U tests.

RESULTS: Among 174 pituitary adenomas, 42 were GH-producing adenomas. Of these, 16 were densely granulated, and 24 were sparsely granulated (two histologic specimens were lost). Signal intensity was evaluated among 153 adenomas. On T2-weighted MR images, hypointensity was seen more commonly in adenomas that produced GH (16 of 40 cases [40%]; P <.001) than in those that did not; hypointensity was nearly exclusive to densely granulated GH-producing adenomas. The amounts of amyloid, fibrous tissue, and iron contained in adenomas demonstrated little relationship with signal intensity. Average suprasellar extension was significantly smaller in adenomas that produced GH (-0.8 mm) than in those that did not (5.3 mm) (P <.001). GH-producing adenomas tended to demonstrate infrasellar extension rather than suprasellar extension. Average sellar depth associated with GH-producing microadenomas (13.3 mm) was significantly greater than for non-GH-producing microadenomas (9.7 mm; P <.001).

CONCLUSION: Characteristic features regarding growth direction and T2 signal intensity can be identified for GH-producing adenomas.