Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) - a rare recently described gastric polyposis syndrome - report of a case.

In rare cases with multiple gastric polyps in the corpus and fundus, a recently described gastric polyposis syndrome called gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) has to be considered. We report on the findings in a patient fulfilling the criteria of this disease.A female patient born in 1977 underwent gastroscopy in 2005 due to recurrent abdominal pain. Endoscopy revealed more than 100 fundic gland polyps in the corpus and fundus. An ileocolonoscopy was inconspicuous. The patient did not take proton pump inhibitors. In follow-up biopsies, fundic gland polyps with low-grade dysplasia were observed. In 2015 gastroscopy with biopsy revealed for the first time high-grade dysplasia in a polyp, and the patient underwent prophylactic gastrectomy.Macroscopic examination of the gastrectomy specimen revealed hundreds of polyps predominantly measuring 3 mm in diameter covering the fundus and corpus. Histology showed fundic gland polyps, mainly covered by normal appearing foveolae. However, several of them were covered by lesions reminiscent of gastric foveolar adenomas with low- and focally high-grade dysplasia. Molecular pathology revealed a point mutation in the adenomatous polyposis coli promotor 1B. These findings in conjunction with the knowledge that the patient's father had died of gastric carcinoma in his 50 s led to the diagnosis of the autosomal dominant syndrome GAPPS, which has hitherto been described in 9 families.