Feline pyloric and duodenal adenoma: A histological and immunohistochemical study

Although pyloric and duodenal adenomas occasionally occur in cats, limited information is currently available on their phenotypes and molecular features. The present study investigated the pathological features of these tumors and the mechanisms underlying their tumorigenesis. Biopsy samples from 8 cats diagnosed with pyloric or duodenal adenomas were examined by histopathology and immunohistochemistry. Normal pyloric and duodenal tissues of cats were assessed for comparison. All cases showed a papillary growth of cuboidal to columnar cells with eosinophilic, ground-glass cytoplasm. Mucin in tumor cells was positive for periodic acid–Schiff and paradoxical concanavalin-A staining, but was negative for Alcian blue. Immunohistochemically, tumor cells were positive for cytokeratin (CK) 19 in 8/8 cases and for CK20 in 5/8 cases, and weakly positive for CD10 in 4/8 cases, CK7 in 3/8 cases, and β-catenin in 2/8 cases. Nuclear accumulation of p53 was not detected in any case. DNA sequencing analysis identified no KRAS or GNAS mutations in the 4/8 cases and 5/8 cases for which the KRAS and GNAS genes could be amplified. The histological and immunohistochemical features of tumor cells were similar to those of mucous neck cells and the pyloric gland of normal feline tissue. The morphology of feline pyloric and duodenal adenomas was consistent with that of pyloric gland adenoma in humans; however, its molecular pathogenesis may differ given the lack of KRAS and GNAS mutations in the feline tumors.

Pyloric, pseudopyloric, and spasmolytic polypeptide-expressing metaplasias in autoimmune gastritis: a case series of 22 Japanese patients

There are two types of pyloric gland-like metaplasia in the corpus of stomach: pyloric and pseudopyloric metaplasias. They show the same morphology as the original pyloric glands in H&E staining. Pseudopyloric metaplasia is positive for pepsinogen (PG) I immunohistochemically, whereas pyloric metaplasia is negative. Recently, spasmolytic polypeptide-expressing metaplasia (SPEM) is proposed for pyloric gland-like metaplasia mainly in animal experiments. SPEM expresses trefoil factor family 2 (TFF2) and is often considered synonymous with pseudopyloric metaplasia. We reviewed consecutive 22 Japanese patients with autoimmune gastritis (AIG) to investigate TFF2 expression in pyloric and pseudopyloric metaplasias by counting all pyloric gland-like glands in biopsy specimens taken from greater curvature of the middle corpus according to the Updated Sydney System. Pyloric metaplasia was seen in all the 22 cases, and pseudopyloric metaplasia was found in 15 cases. Of 1567 pyloric gland-like glands in all the cases, 1381 (88.1%) glands were pyloric metaplasia glands, and the remaining 186 (11.9%) glands were pseudopyloric metaplasia glands. TFF2 expression was observed in pyloric or pseudopyloric metaplasia glands in 20 cases. TFF2 expression was recognized in 409 of 1381 (26.9%) pyloric metaplasia glands and 27 of 186 (14.5%) pseudopyloric metaplasia glands (P<0.01, chi-square test). In conclusion, SPEM was not always the same as pseudopyloric metaplasia in human AIG, and the majority of metaplasia in AIG was not pseudopyloric but pyloric metaplasia.