lump in armpit

I am 35 years old.  I have a rather large lump (golfball-sized and somewhat soft) in my armpit that appeared two weeks ago.  I believe it to be a lymph node because this area has been swelling up and going back down for about a year, but never getting this big.  When the lump swells up it is tender to the touch, but not independently painful.  I don't have any other symptoms that I associate with this lump.  My doctor has started me on an antibiotic because she is convinced it is cat scratch disease - I am not convinced.  I had mammogram (my first), chest xray and an ultrasound.  While my doctor said they were OK, the radiology clinic sent me a letter saying the ultrasound showed a suspicious area that should be re-checked in 3 months.  During the ultrasound, the technician focused on a spot in the lower area of my left breast - the same side with the lump in the armpit.  Are these related?  The information on the internet about lymphoma scares me because I get night sweats too.  At my next appointment I intend to insist that my doctor arrange to have fluid drawn from this lump and tested.  Any input?

Thanks, Laurie

[CCF-RN,MSN-JS]

Dear Laurie, Although your symptoms can be associated with cat scratch disease, it makes sense to have this lymph node biopsied to determine the reason for the swelling.  It is unclear as to whether this has any relationship to the suspicious area reported on the ultrasound.  If you are uncomfortable with waiting you may want to be evaluated by a physician specializing in breast disease.