This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stomach, Subject name: Pathology
[{'content': 'A 35-year-old man undergoes gastrectomy for gastric carcinoma. Gross examination of the resected stomach reveals diffuse thickening without a discrete mass lesion. Microscopic exam shows an infiltration of signet-ring cells dispersed singly. Family history reveals that his father had a similar cancer at a young age. What gene is most likely to be mutated in this patient and his father? \nSelect and explain. \nA. APC, B. CDH1, C. PMS2, D. p53', 'role': 'user'}, {'content': 'Answer: B \nExplanation: - Mutation in CDH1, the gene encoding the cellular adhesion protein E-cadherin. - E-cadherin mutations account for a significant propoion of familial gastric cancers and Lobular carcinoma of the breast. OTHER OPTIONS: - APC is mutated in the majority of colorectal adenocarcinomas & intestinal type of gastric cancer. - MSH2 and PMS2 are both mismatch repair genes are mutated in Lynch syndrome - p53 is mutated in Li Fraumeni syndrome.', 'role': 'assistant'}]