Clinicopathologic Characteristics and Mucin Expression in Brunner's Gland Proliferating Lesions

Brunner's gland proliferating lesions, termed Brunner's gland hamartoma, hyperplasia, or adenoma, is regarded as a benign condition. However, cancerous changes have been reported in Brunner's gland proliferating lesions. The purpose of this study was to define the characteristic features of Brunner's gland proliferating lesions and evaluate any observed cancerous changes. We analysed clinicopathologic features and mucin expression in 25 Brunner's gland proliferating lesions. Brunner's gland proliferating lesions were categorized as Brunner's gland hamartoma or hyperplasia according to their tissue components. Brunner's gland hamartoma commonly occurred in the duodenal bulb and exhibited a polypoid appearance, while Brunner's gland hyperplasia was primarily observed in the second portion of duodenum as a submucosal mass and was accompanied by symptoms more frequently than Brunner's gland hamartoma. The Brunner's glands in Brunner's gland proliferating lesions exhibited various morphologic characteristics, from normal-appearing glands to sclerotic glandular foci with atypia. Changes in MUC5 expression observed in both sclerotic glandular foci and dilated Brunner's glands suggest that they might share a common mechanism and are associated with gastric foveolar metaplasia. These findings indicate that most Brunner's gland proliferating lesions are either hamartoma or hyperplasia, and that true neoplastic Brunner's gland proliferating lesions are very rare. Thus, Brunner's gland adenomas or carcinomas arising in Brunner's gland proliferating lesions should be confirmed by ancillary tests, including immunostaining or molecular analysis, in addition to morphological criteria.