•When did you first notice the lump?
•Has it changed in size?
•Does it hurt?
•Have you noticed anything that seems to make it worse?
•Do you have any other symptoms of illness?
•Are you breast-feeding?

If the answers to these questions don’t shed any light on the situation, the doctor may ask you to have an ultrasound, CT scan, and/or a mammogram, any of which will provide a better view of just what the lump consists of. You may also need fine needle aspiration, a process that draws fluid from the affected lymph node for examination. Finally, you may need a biopsy, if all the other tests prove inconclusive.

Q. So, let’s see if I have this right. If it’s a painful, soft lump, and maybe the skin around it is red, and it seems to be growing, it’s probably from an infection. I should see the doctor for some antibiotics.

And if it’s a hard, painless lump, one that seems fixed in place (and may feel like it’s connected to other hard lumps); and it seems to be staying the same size day to day (not growing quickly), I should see the doctor to rule out cancer.

Right?

A. Exactly right. You need to see a doctor about any underarm lump that a) seems to be worsening quickly, or b) doesn’t disappear within a couple of weeks. The only time you don’t need to pursue diagnosis and treatment of a lump in your armpit is if it disappears entirely, and doesn’t return.