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: Pathology
Single most important prognostic indicator of colorectal carcinoma is - 
Select and explain. 
A. CEA titres, B. Degree of atypia, C. Size of tumor, D. Extent of tumour
D: Extent of tumour
Answer: D: Extent of tumour 
Explanation: The single most important prognostic indicator of colorectal carcinoma is the extent of the tumor at the time of diagnosis, the so-called stage.