This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Most common type of gastric tumor in adults: \nSelect and explain. \nA. Adenocarcinoma, B. Stromal tumor, C. Leiomyosarcoma, D. Lymphoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: About 85% of stomach cancers are adenocarcinomas, with 15% due to lymphomas, gastrointestinal stromal tumors (GISTs), and leiomyosarcomas.\xa0\nGastric\xa0adenocarcinomas\xa0may\xa0be\xa0subdivided into two pathologically defined categories:\n\nDiffuse type, in which cell cohesion\xa0is\xa0absent,\xa0so\xa0that\xa0individual\xa0cells\xa0infiltrate and thicken the stomach wall without forming a discrete mass.\nIntestinal type, characterized\xa0by\xa0cohesive\xa0neoplastic\xa0cells\xa0that\xa0form\xa0gland-like\xa0tubular\xa0structures.\xa0\n\nThe diffuse carcinomas occur more often in younger patients, develop throughout the stomach (including the cardia), result in a loss of distensibility of the gastric wall (so-called linitis plastica, or “leather bottle” appearance), and carry a poorer prognosis.\nReference: Harrison’s P R I N C I P L E S\xa0 \xa0O F I N T E R N A L M E D I C I N E 20th edition page no 568', 'role': 'assistant'}]