Can doctors tell if this is breast cancer without the biopsy result?

my sister found a lump in her breast and saw her doctor who referred her to a breast clinic for tests and once there she was given a scan,mammogram and had a biopsy,when she came home she said that after the scan and mammogram the doctors said it was cancer and was malignant but she had to wait a week for the biopsy results which she is getting later today.i along with my family and friends fully support her and are very upset knowing she has cancer especially as she is only 35 but my mother-in-law seems to think that the doctors will not know if the lump is malignant until she has the biopsy result and basically accused my sister of either lying or not knowing what she is talking about and her words have really upset me as i know my sister would never lie about this so i am hoping to prove to my in-laws that infact you can find out before the biopsy results so any help would be great,thanks