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
Esophageal carcinoma what is the most impoant prognostic indicator? 
Select and explain. 
A. Length of involvement, B. Depth of invasion, C. Histological grading, D. Immunohistochemistry
B: Depth of invasion
Answer: B: Depth of invasion 
Explanation: 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.