Bump Under Armpit

In early April I had a lump appear under my armpit.  It was slightly painful, so I saw my primary care physician.  She said it felt like a cyst attached to the skin and wasnt attached to the lymph node, and so she gave me antibiotics.  I have acne elsewhere so she suspected that it could be a pimple.  The antibiotics made it go away for about three weeks, but last night, out of nowhere, it reappeared and came back more red and painful.  Its about the same size as it was before.  She said to return if it came back more inflamed and painful.  This time I'm going to see my dermatologist, and I have an appointment with her in two weeks.  It certainly feels like a pimple, but it doesnt come to a head where it could be popped.  I dont shave my armpits and I haven't switched deoderants lately.  I know my dermatologist will ultimately decide what to do, but is it still possible that its a pimple, even though it returned after it went away with antibiotics?  Could a bump like this be cancerous, even though its not attached to the lymph node?  

[Alan Rockoff, MD]

Not cancer, for sure.  It may be a cyst that's getting repeatedly infected.  If so, it may need to be lanced, and might conceivably be a candidate for being surgically excised.  Until you see the dermatologist, I suggest hot compresses and external applications of bacitracin or neosporin ointment.

Best.

Dr. Rockoff