Post written by Yusaku Shimamoto, MD, from the Department of Gastrointestinal Oncology, Osaka International Cancer Institute, Osaka, Japan.

Gastric neoplasms in familial adenomatous polyposis (FAP) patients were classified into 4 types based on endoscopic findings. Then, their clinical, histopathologic, and genetic features were investigated.

Gastric neoplasms in patients with FAP are endoscopically and histopathologically characteristic compared to sporadic gastric neoplasms but not well recognized because of a lack of comprehensive reports. In this study, gastric neoplasms of FAP patients were classified into 4 types based on endoscopic findings, and their immunologic phenotypes were different. It was suggested that heterogeneity may be present. This classification can not only be useful for the detection but also lead to an understanding of gastric neoplasms in FAP patients.

Types of gastric neoplasms:

・Type L; reddish and depressed lesions in the L region

・Type UM-W; whitish and elevated lesions in the UM region

・Type UM-T; translucent and elevated lesions in the UM region

・Type UM-R; same to reddish and elevated lesions in the UM region

A representative neoplasm was selected for each of the 56 patients in this study, and 93% were classifiable into either type. Therefore, recognizing these types facilitates the detection of gastric neoplasms in FAP patients. Furthermore, they differed in clinical and immunologic phenotypes depending on the type, which suggests that gastric neoplasms may differ in nature.

Although more than 90% of gastric neoplasms are caused by Helicobacter pylori, FAP patients with APC germline variant develop gastric neoplasms at a high rate regardless of the Helicobacter pylori infection and can be fatal. We hope that this classification will help early detection and will be a clue to elucidate the pathophysiology.

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