| [ Summary ] |
Gastric adenocarcinoma of the fundic gland type (GAFG) was recently proposed as a new and rare variant of gastric adenocarcinoma. GAFG has distinct clinicopathological and immunohistochemical features. GAFG is characterized by positive immunohistochemical staining for pepsinogen‒I (a marker of chief cells) and/or H+/K+‒ATPase (a marker of parietal cells), and is not associated with Helicobacter pylori infection. Histopathologically, GAFG is classified into pure GAFG and gastric adenocarcinoma of fundic gland mucosal type (GAFGM), which exhibits differentiation toward gastric foveolar epithelium in addition to fundic gland differentiation. GAFG has distinct endoscopic characteristics on white light endoscopy (WLE) and magnifying endoscopy with narrow‒band imaging (ME‒NBI). The endoscopic features on WLE are 1) a submucosal tumor shape, 2) a whitish color, 3) dilated vessels with branching architecture, and 4) background mucosa without atrophic change. The endoscopic features on ME‒NBI are 1) an indistinct line of demarcation between the lesion and the surrounding mucosa, 2) dilatation of the crypt opening, 3) dilatation of the intervening part between the crypts, and 4) microvessels without distinct irregularity. In addition, ME‒NBI may be useful for the cancer diagnosis of GAFGM and for discrimination between pure GAFG and GAFGM. However, the endoscopic diagnosis of GAFG is considered difficult for endoscopists who have no experience in GAFG cases. The endoscopic diagnosis of GAFG could be conducted by recognizing these endoscopic features of GAFG with WLE and ME‒NBI. In addition, to elucidate the natural history of GAFG by assessing the classification based on the grade of atypia and cell differentiation, further investigation should include collecting cases based on these endoscopic features and on the correct pathological diagnosis of GAFG. |