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
Gleason's classification used for - 
Select and explain. 
A. Carcinoma breast, B. Carcinoma prostate, C. Carcinoma pancreas, D. Carcinoma rectum
B: Carcinoma prostate
Answer: B: Carcinoma prostate 
Explanation: Several grading systems have been described for prostatic carcinoma, of which the Gleason system is the best.