Breast lump

Hi everyone

I am new to the group. I have a lump in my left breast I have no other symptoms and it isn't painful. Went to the doctors today who said it was pretty big and will refer me to the breast clinic. 

I'm not sure what I want to ask really, as I know they obviously want to rule out cancer. I suppose I am worrying more now, I thought if the doctor thought it was ok nothing else would be done. Can doctors tell if it's cancer or do they really not though until it's been tested ?