This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
"Adenoma - carcinoma sequence" is seen in 
Select and explain. 
A. Follicular thyroid carcinoma, B. Carcinoma gall bladder, C. Carcinoma stomach, D. Carcinoma colon
D: Carcinoma colon
Answer: D: Carcinoma colon 
Explanation: (Carcinoma colon) (1177-LB) (1179-B &L 25th)Adenocarcinoma of the colon: microscopically the neoplasm is a columnar cell carcinoma originating in the colonic epithelium. Macroscopically, the tumour may take one of four forms. Type 4 is the least malignant form* It is likely that all carcinomas start as benign adenoma the so called "adenoma-carcinoma sequence"* The annular variety tends to give rise to obstructive symptoms whereas the others more commonly willpresent with bleeding.* Tumours are more common in the left colon and rectum.