This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
[{'content': 'Most common gallbladder malignancy \nSelect and explain. \nA. Adenocarcinoma, B. Squamous cell carcinoma, C. Mucinous cystadenoma, D. Serous cystadenoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Histological types of gallbladder carcinoma Diffuse infiltrative type : MC type Nodular or mass forming Papillary: Exhibits polypoid or cauliflower appearance and have best prognosis Adenocarcinoma : MC histological subtype of CA GB In CA GB Direct hepatic invasion : 59% Lymph node metastasis : 45% Perineural invasion : 42% Ref: Sabiston 20th edition Pgno :1512-1514', 'role': 'assistant'}]