48 Gastric Adenomyoma: A Rare Subepithelial Distal Stomach Tumor

Abstract

Gastric adenomyoma is a benign, rare subepithelial tumor composed of mucosal elements and a prominent smooth muscle stroma commonly found in the stomach or duodenum occurring from the ages of 1 week to 81 years. Many cases are incidental findings on endoscopic examination or computed tomography (CT) scans; however, gastric adenomyoma can produce peptic-type ulcers and gastrointestinal (GI) tract bleeding. It is very difficult to diagnose this entity radiographically with non-specific CT findings; thus it is noteworthy for radiologists to recall this benign tumor. Whenever there is a gastric cystic subepithelial mass involving the distal portion of the stomach, it is important to remember gastric cystic adenomyoma. A 30-year-old woman presented to a teaching hospital in south Texas with abdominal pain. A CT scan showed narrowing of the distal stomach and antrum and a cystic lesion suggestive of a stromal tumor. A gastroduodenectomy specimen was obtained and processed at the surgical anatomic pathology laboratory. H&E and immunohistochemistry (IHC) studies were performed on formalin-fixed paraffin-embedded (FFPE) tissue. Microscopic examination demonstrates a segment of stomach with gastric antral type mucosa and an underlying mass forming lesion consisting of scattered gastric type glands with focal metaplastic changes admixed with bundles of smooth muscle. Focally active duodenitis is present overlying the lesional tissue. Helicobacter pylori-like organisms are not identified. An immunohistochemical stain for CD117 is negative in the stromal cells. CD10 is positive in scattered inflammatory cells and negative in the stroma cells surrounding the entrapped glands. PAX-8 is negative in the entrapped glands, and CD34 highlights scatter vascular channels. There is no dysplasia or malignancy. This is a rare case of gastric adenomyoma, a benign hamartomatous tumor involving the antrum that must be considered when evaluating gastric subepithelial masses involving the distal portion of the stomach.