Brunner's Gland Hyperplasia and Hamartoma

Normal Brunner's Glands

• Brunner's glands are mucus-secreting acinar glands located in the deep mucosa and submucosa of the duodenum, emptying into the crypts of  Lieberkühn. They are most numerous in the duodenal bulb and secrete mucus, pepsinogen, and urogastrone in response to acid stimulation. At light microscopy, the cells of Brunner's glands are eosinophilic with clear cytoplasm, and they typically contain basally oriented nuclei

• A rare condition. The pathogenesis remains poorly understood. Gland stimulation by gastric hyperacidity was originally thought to induce hyperplasia; however, only 45% of patients demonstrate hyperacidity and 20% have low gastric acidity. Other suggested mechanisms include proliferation in response to local irritation or excessive parasympathetic activity.

• Frequently asymptomatic.

• May manifest as solitary or multiple nodules that are typically less than 5 mm in diameter. Endoscopically, Brunner's gland hyperplasia appears as submucosal nodules in the first or second portion of the duodenum.

• Histologically present as multiple small polypoid or nodular lesions composed of excessive Brunner's glands separated by fibrous septa, often <5mm. If greater than 5 mm, it is often called a hamartoma.

• Differential diagnosis: multiple adenomas of familial adenomatous polyposis, hamartomas in Peutz-Jeghers syndrome, nodular lymphoid hyperplasia, heterotopia, nodular duodenitis, carcinoid tumors, and metastatic disease.

• Brunner's gland hyperplasia and hamartoma are infrequently encountered polypoid nodules and masses in the proximal duodenum. They account for approximately 5% of all duodenal masses

Brunner's gland hamartomas

• Middle age with no sex predominance.

• May cause abdominal pain, duodenal obstruction, gastrointestinal hemorrhage, duodenal intussusception, and obstruction of the common bile duct or pancreatic duct.

• Most common location is the posterior wall of the duodenum near the junction of the first and second portions.

• May present as a submucosal mass that may have a pedicle. Grossly, Brunner's gland hamartomas have a smooth surface and tend to be well-circumscribed, solitary polyps that can be sessile or pedunculated. They are pink and tan on cut surface with a lobular appearance due to fibrous septa.

• Histological features: a solitary mass that contains a mixture of acini, ducts, smooth muscle, adipose tissue, and lymphoid tissue, occasionally contain heterotopic pancreatic acini and ducts. Often >5mm. Histological features favoring hamartoma include lack of encapsulation; admixture of muscular, glandular, and adipose tissues; presence of continuous sheets of Brunner's glands from the submucosa through the body of the tumor; and lack of any cellular atypia. The presence of both ductal and glandular components is a further evidence of a hamartomatous origin, features which are unusual in hyperplasia or neoplasia.

Brunner's gland adenoma (Brunneroma)

• lesions that are histologically similar to Brunner's gland hamartoma. Because these lesions do not have features of cellular atypia, the term "Brunner's gland adenoma" has fallen out of favor.

AJR 2006; 187:715-722