I was exercising and noticed a small lump (about the size of a large pea) under my left armpit. It doesn't hurt to press on it, but I can't tell if it is moveable. I did have some itching under my armpit a few weeks ago. I didn't think anything of it. A friend in the medical profession told me to watch it for 30 days (changes in size, pain,...). I am concerned and wonder if I should wait that long. What would be the first step to determine if this is cancer or just a benign cyst?

I don't know your age, but I would not take any chances I would go see a doctor. It may not be anything, but why take the chance. I had a lump under my arm pit last year and waited to see a doctor, until we had health insurnace. I had a mammogram on Nov 11, 2006, and since then have had to have a mastectomy, and have to start chemo in Jan. Please take my advice and see a doctor. I am not trying to scare you, I am just concerned and would not wish what I am going through on any one.

michelleono ,
The lump could be anything from a benign lymph node, ingrown hair to breast ca. If you are concerned, see a doctor and get an ultrasound. Lumps should always be ultrasounded if they are abnormal. If you are premenopausal I would not wait to long to see a doctor if this changes.