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: Medicine
Achalasia is associated with increased risk of ...... malignancy: 
Select and explain. 
A. Squamous cell carcinoma esophagus, B. Adenocarcinoma esophagus, C. Bronchogenic carcinoma, D. Bronchial adenoma
A: Squamous cell carcinoma esophagus
Answer: A: Squamous cell carcinoma esophagus 
Explanation: Prolonged stasis esophagitis in achalasia is the likely explanation for the association between achalasia and esophageal squamous cell cancer. Squamous cell cancer esophagus risk is increased 17-fold in achalasia cardia. Ref: Harrison, Edition-18, Page-2432