Prediction of Consistency of Pituitary Adenomas by Magnetic Resonance Imaging

Objective: Pituitary adenomas are typically soft with occasional cases of firm fibrous tumors. The prevalence of fibrous adenomas is approximately 5 to 13%. These tumors are defined as difficult to remove by curettage or suction. Their surgical resection can be challenging with usually higher rate of incomplete resection and need for multiple surgeries. Predicting fibrous adenomas by magnetic resonance (MR) imaging is usually difficult and unreliable. We propose a new method based on MR T2 sequence intensity ratios of the tumor with reference to the cerebellar peduncle with a goal of finding a method to predict these cases on preoperative imaging.

Methods: The MR images of 34 consecutive patients who underwent nonsecreting macroadenoma resection were evaluated by a blinded radiologist. Using MR T2-weighted sequence, regions of interest were sampled from the adenoma and the cerebellar peduncle, and the ratio was calculated. Intraoperatively, tumors were graded prospectively for their consistency as soft or fibrous.

Results: There were 27 soft and 7 fibrous tumors. Unpaired t-test for these ratios was found to be statistically significant (p < 0.0240; 95% CI, − 0.8229 to −0.06207). Mean values for soft tumors was found to be 1.918 (SEM = 0.08212); thus mean range was 1.84 to 2.00. Mean values for firm tumors was found to be 1.475 (SEM = 0.1179); thus, mean range was 1.36 to 1.59. Using these results, we suggest a ratio > 1.8 suggests soft consistency; meanwhile, a ratio < 1.6 suggests firm consistency.

Conclusion: Fibrous adenomas are typically diagnosed intraoperatively. However, their resection can be technically challenging. Using T2 intensity ratios of tumor to cerebellar peduncle on routine preoperative MR imaging will allow identification of these cases on preoperative imaging. The surgeon can then be better prepared for the surgical resection of these cases.