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
Which type of malignancy is found in anorectal fistulaa) Sq. cell Cab) Transitional Cell Cac) Adeno Cad) Columnar Ca 
Select and explain. 
A. a, B. bc, C. ac, D. b
C: ac
Answer: C: ac 
Explanation: • MC type of carcinoma to arise in fistula-in-ano: Colloid carcinoma (44%) > Squamous cell carcinoma (34%) > Adenocarcinoma (22%)
• Clue to early diagnosis is the appearance of mucin globules in Fistulotomy or fistulectomy specimens