Approximately 90% of neoplasms found in the sellar region are adenoma of the pituitary gland. The use of frozen sections for the diagnosis of pituitary adenomas has an accuracy of 90% and is useful in evaluating complete tumor removal. However, it is sometimes difficult to diagnose pituitary adenomas using frozen sections because of the small sample size and marked artifact, and the contiguity of the pituitary adenoma with normal pituitary gland tissue. In this study, we evaluated the use of our modified reticulin stain to make correct decision in frozen section with reduced stain time and investigated the objective diagnostic criteria of pituitary adenoma with reticulin stain. We used Gomori's silver impregnation methods to stain reticulin fibers in frozen pituitary gland sections of 36 samples from 24 patients. We modified the conventional staining method by reducing the overall staining time. We diagnosed pituitary lesion according to our interpretation criteria and compared the results to those of the conventional method and findings of hematoxylin and eosin-stained slides. Reticulin fiber staining of normal adenohypophysis outlines the supporting stroma around the blood vessels and shows regular of the gland meshwork interconnecting the capillaries. In contrast, reticulin fiber staining of the adenomatous tissue shows loss of meshwork or frequent fragmentation. Our modified reticulin stain is more rapid than the established method and shows similar levels of accuracy. Independent evaluation by two pathologists showed discrepancies in diagnosis in four out of 36 cases with modified reticulin stain. Our rapid modified reticulin staining method for frozen sections may be useful as a diagnostic tool for pituitary adenomas and can complement routine hematoxylin and eosin staining.