Pyloric adenoma in the transverse colon

An 88-year-old male who attended due to a right inguinal tumour, constitutional symptoms and positive occult blood in stool. A colonoscopy was performed, finding a 1.5 cm sessile polyp of adenomatous appearance in the transverse colon, which was excised (Fig. 1).

Figure 1.

Endoscopic image of a pyloric gland adenoma in the transverse colon.

The histological study found a proliferation of the adenomatous pattern made up of gastric glands of pyloric appearance (Fig. 2). The immunohistochemical study (Fig. 3) confirmed the expression of gastric mucins (MUC5 superficially and MUC6 in the deep glands), but was negative for intestinal mucins (MUC2). The diagnosis was pyloric gland adenoma without dysplasia.

Figure 2.

Anatomopathological image showing a polypoid structure with medium-sized tubular glands, some of them dilated, that appear to be coated in cylindrical epithelium with eosinophilic cytoplasm and isomorphic nuclei.

Figure 3.

Immunohistochemical staining showing expression of MUC5 superficially and MUC6 in the deep glands.

Discussion

Pyloric adenoma is an uncommon neoplasia of the gastric mucosa that can originate in heterotopic gastric mucosa. It appearance in the lower digestive tract is exceptionally rare.^1,2 The most extensive published review¹ covers 33 cases of gastric heterotopy in the colon, in particular in the rectum (78%), with no cases in the transverse colon. Of the 33 cases, just five were pyloric gland adenoma, two of these with foci of adenocarcinoma. The true risk of malignancy of this lesion is unknown due to its scarcity, but it seems clear that there is a probable link with KRAS mutations.³