EARLY GASTRIC ADENOCARCINOMA OF THE FUNDIC GLAND (CHIEF CELL PREDOMINANT TYPE): A NEW CHALLENGE FOR AN ENDOSCOPIST AND A PATHOLOGIST

A 65-year-old female patient was referred to Yaroslavl Regional Cancer Hospital for screening upper gastrointestinal endoscopy. A 6 mm elevated lesion at the greater curvature of the upper part of gastric body was detected. The lesion had a poorly demarcated border and a whitish regular surface with dilated branching vessels by conventional white light imaging (WLI) endoscopy. Magnifying narrow-band imaging (M-NBI) observation of the lesion identified the indistinct demarcation line with a regular microsurface and a microvessel pattern. No atrophic changes were confirmed at the background gastric mucosa, Helicobacter pylori infection was not detected. Target forceps biopsy was taken for histological assessment of the lesion. Histology showed carcinoma mimicking the normal gastric fundic glands with an irregular branching structure. Endoscopic submucosal dissection (ESD) was performed for en-bloc resection of the lesion. Histological examination of the post-ESD specimen showed well-differentiated gastric adenocarcinoma of fundic gland (GAFG) with submucosal invasion < 500 micrometers (sm1). The tumor was located in the deep region of the fundic gland and was totally covered by non-neoplastic foveolar epithelium. Immunohistochemically, the lesion had diffuse positivity for pepsinogen I (chief cell differentiation), and focal positivity for H+/K+-ATPase (parietal cell differentiation) suggesting a chief cell-predominant type of a cancer. Endoscopic resection was assessed as complete (R0) with negative horizontal and vertical margins of the specimen, no lymphatic and venous infiltration were found. GAFG is a rarely diagnosed gastric neoplasm of oxyntic mucosa which is considered to be a limitation for M-NBI diagnosis and therefore should be identified by careful WLI endoscopy only [Ueyama et al., 2014]. A recent literature search through PubMed was conducted to obtain 111 cases of GAFG (mainly from Japan) [ Benedict et al., 2018]. To the best of our knowledge this is the first report of this type of gastric cancer in Russia and Europe.