Which of the following test is unable to differentiate between 'in situ' breast cancer and invasive disease

"FNAC is the least invasive technique for obtaining a cell diagnosis and is very accurate if both operator and cytologists are experienced. However false negatives do occur, mainly through sampling error, and invasive cancer cannot be distinguished from 'in situ' disease. A 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. This is impoant before commencing neoadjuvant therapy." Bailey and Love Ref : Bailey & Love 26/e p 800