This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gynaecological oncology, Subject name: Gynaecology & Obstetrics
[{'content': 'The following primary tumours are common in the vulva except : \nSelect and explain. \nA. Adenocarcinoma, B. Basal cell carcinoma, C. Choriocarcinoma, D. Squamous cell carcinoma', 'role': 'user'}, {'content': "Answer: C \nExplanation: Invasive lesions of vulva : Squamous cell carcinoma--most common 90% Melanoma 1-5% Adenocarcinoma 1% Sarcoma 2% Rodent ulcer or basal cell carcinoma 1%. Reference: Shaw's Textbook of Gynaecology 16th edition page no 475", 'role': 'assistant'}]