Endocrine Abstracts

Objective: We examined whether sequential enhancement patterns of pituitary microadenomas on dynamic MRI correlates with different subtypes of pituitary tumors.

Materials and methods: Patients with pituitary microadenomas imaged via dynamic MRI between years 2000 and 2012 were included. The intensity of the adenoma and of normal gland at each time point in the dynamic sequence was measured by drawing a region of interest (ROI) on both the normal pituitary gland and the tumor. Measurements included: enhancement ratio (ER), defined as the ratio of the tissue at time (t) vs the baseline (t=0); pituitary-adenoma ratio (PAR), which is the ratio of the normal anterior pituitary lobe to that of pituitary adenoma; and, the speed to reach the peak intensity. From these data tumors were classified as early, simultaneous or late (peak before, at the same time or after normal pituitary tissue, respectively). Correlation between the enhancement pattern and the tumor subtype was analyzed using Pearson product-moment correlation coefficients and logistic regression analysis.

Results: A total of 118 patients had functional adenomas, while 47 patients had nonfunctional adenomas. We found that the enhancement levels in all pituitary adenomas subtypes were lower than those in normal pituitary tissue (P<0.0001). There was a significant correlation between the enhancement patterns of functioning vs nonfunctioning tumors (P=0.0397) and between the four tumor subtypes (P=0.0039). Functional adenomas usually exhibited simultaneous or late enhancement pattern while nonfunctional adenomas showed early enhancement pattern. The time to reach peak enhancement in normal pituitary tissue was shorter nonfunctioning adenomas (P=0.0082) and GH tumor group (P=0.0042).

Conclusion: Our study is the first to show significant correlation between enhancement pattern and pituitary adenoma subtype. This finding can provide supplemental information in differential diagnosis of pituitary microadenomas as well as guide future studies of appropriate timing of image acquisition according to tumor subtypes.