This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rectum and anal canal, Subject name: Surgery
Commonest type of carcinoma anal canal is: 
Select and explain. 
A. Adenocarcinoma, B. Squamous cell carcinoma, C. Adenocanthoma, D. Papillary type
B: Squamous cell carcinoma
Answer: B: Squamous cell carcinoma 
Explanation: CARCINOMA ANAL CANAL MC type of CA anal canal : SCC > BCC > Melanoma Median age at diagnosis :60 years MC symptom : Bleeding PR MC site of metastasis: Lung MC site of LN metastasis : Inguinal LNs