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
[{'content': 'Achalasia is associated with increased risk of ...... malignancy: \nSelect and explain. \nA. Squamous cell carcinoma esophagus, B. Adenocarcinoma esophagus, C. Bronchogenic carcinoma, D. Bronchial adenoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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', 'role': 'assistant'}]