This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lung Tumor, Subject name: Pathology
Least common cause of clubbing is: 
Select and explain. 
A. Adenocarcinoma, B. Squamous cell cancer, C. Small cell cancer, D. Mesothelioma
C: Small cell cancer
Answer: C: Small cell cancer 
Explanation: Lung cancer is the most common cause of clubbing . Most common with adenocarcinoma and is least common with small cell lung cancer.