Does this ring a bell.What could it be??

Hi everyone new to the forum tonight just wondered if anyone could offer any advice about the following?
My mum had breast cancer some 24 years ago. She had the lump removed and radiotherapy.
For about the last year she has had what I can only describe as a little spot on the scar tissue. She has shown it to the doctor regularly, and she wasn’t particularly worried. Last month this spot changed into something like a wart in appearance. On friday it fell off and my mum had quite a bit of browm discharge from it. She went to GP who thought it was an infection and gave her penicilin.She got an unexpected call on friday night telling her to go to the breast clinic today.
The breast doctor had told her it isn’t an infection and she must go for a mamogram and biopsy this week.
Alarm bells have started to ring and we are all worried sick. Has anyone else experienced this