Brunner's gland cyst: a clinicopathological study of 25 cases highlighting an underappreciated lesion

Brunner's gland cysts are rare, benign lesions of the duodenum usually seen as incidental, polypoid or cystic lesions of the duodenum. We present a series of 25 cases of Brunner's gland cyst, the largest case series to date. All the cases were identified during endoscopic assessment for unrelated causes. The mean age of the patients was 66.2 years and the sex ratio was approximately equal. Most were detected as a small (3-10 mm) polypoid lesion in the second part of the duodenum, away from the ampulla. Most of the cysts were unilocular and all were lined by undulating, cytologically bland cuboidal to columnar cells with clear cytoplasm and small, basal nuclei. No mitotic activity or proliferative activity was seen. No recurrence was noted, despite incomplete removal in many cases. We agree with the hypothesis that Brunner's gland cysts are likely to be caused by local obstruction to the draining duct of Brunner's glands.