If you want truly Professional advice then you should post your question on the "Expert" Forum where Dr.s from the Cleveland Clinic answer. This Forum is actually a pt. to pt. discussion Forum even though there are some who are noted to be Physicians ... they are not a part of or employed by The Cleveland Clinic.
It is most unlikely that they will find cancer after surgery. If they have completed the core biopsy and got a benign result well then I would say you mostly likely dont have anything to worry about. However I am sure they will send the lump to the lab for a full pathology report just to be 100% sure.
I think you have posted your questions on the wrong forum. There is another forum for questions to doctors. This forum is normally posted by other women like us and lucky for us a number of doctors come on the forum of their own free will to offer advise and support when they can. Hopefully one of the doctors can give you a better answer to your question.