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: Surgery
[{'content': "Which of the following test is unable to differentiate between 'in situ' breast cancer and invasive disease: \nSelect and explain. \nA. Core needle biopsy, B. FNAC, C. Excisional biopsy, D. None", 'role': 'user'}, {'content': 'Answer: B \nExplanation: "FNAC is the least invasive technique for obtaining a cell diagnosis and is very accurate if both operator and cytologists are experienced.\nHowever false negatives do occur, mainly through sampling error, and invasive cancer cannot be distinguished from \'in situ\' disease.\nA histological specimen taken by core biopsy allows a definitive preoperative diagnosis, differentiates between duct carcinoma in situ (DCIS) and invasive disease and also allows the tumor to be stained for receptor status.\nThis is important before commencing neoadjuvant therapy." Bailey and Love', 'role': 'assistant'}]