Swollen Gland in Armpit

I am  30 years old and I am 24 weeks pregnant.  I have a pea size lump in my right armpit.  It is painful to the touch and as much as I can recall, it seems to come only with preganacy (pregnancy).  Or it gets smaller when I am not pregnant. Is this a sweat gland that is swollen or could it be cancer?

[CCF-RN,MSN-rf]

Dear acgs:  Based on your question, it sounds like this has appeared before (in prior pregnancies?).  If this is the case, then it is very unlikely that this is cancer.  Also, breast cancer is not typically painful.  Having said this, you should have your doctor check it out, just to be on the safe side.

[surgeon]

Highly unlikely to be cancer. A sweat gland, or other skin cyst is possible, as well as an island of ectopic breast tissue, meaning breast tissue located outside the breast; the armpit is a very common location for that to occur. You should have your doctor check it at your next visit.