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: Surgery
[{'content': 'Esophageal carcinoma what is the most impoant prognostic indicator? \nSelect and explain. \nA. Length of involvement, B. Depth of invasion, C. Histological grading, D. Immunohistochemistry', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer- B. Depth of invasionThe depth of invasion of the tumor through the wall of esophagus, is the most impoant prognostic indicator, with considerable independent prognostic significance.', 'role': 'assistant'}]