What is a biopsy, and why do I need one?

It is taking a small piece of the lump so it can be looked at under a microscope. A scan can show us that something is there. Only a biopsy can tell us what it is.

It is also where we learn the details that choose your treatment, including whether particular drugs will work. That is why we sometimes repeat one later. Ask how long the result takes, because the wait is the hard part.

Written by two physicians. Checked against patient information from the US National Cancer Institute and Cancer Research UK.