This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': 'Esophageal carcinoma what is the most important prognostic indicator? \nSelect and explain. \nA. Length of involvement, B. Depth of invasion, C. Histological grading, D. Immunohistochemistry', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Depth of invasion Prognostic indicators in esophageal carcinoma:* The depth of invasion of the tumor through the wall of esophagus, is the most important prognostic indicator, with considerable independent prognostic significance.* Presence or absence of lymph nodal metastases is a significant and independent indicator of prognosis.Other prognostic indicators:* Presence or absence of distant metastases* Resection margins* Serosal or peritoneal involvement* T1 subclassification* Vascular invasion", 'role': 'assistant'}]