Male, 46, non-painful but growing lump in left armpit

[HotRodMike]

I woke up one day and my armpit itched and I felt a small swollen area about the size of a pea, I didn't think much of it. I just put some Triamcinolone cream on it and thought it would go away. By the next day I noticed that it was bigger, not painful, but definitely bigger...about the size of a marble. I decided to go to the doctor on day 3. The P.A (physicians assistant) came in, asked if it hurt, I said no...its just a little itchy and more annoying than anything. She poked it with her finger and said "its probably nothing...and definitely nothing severe". She prescribed a 10 day course of Bactrim. I have now been on it for 2 days (the lump is now 5 days old), the lump is bigger again, but still not painful. I decided to do some reading online and everything I read says that if the lump was painful and moved under the skin it was probably nothing BUT...if it was firm, not painful, stayed in place and grew at a fairly fast rate..it could very well be cancer? Mine is everything they said. I am scared to death! Are my doctors (or their assistants) not too bright? How can they not know what I found out on the internet? They always say that the faster you catch cancer, the better off you are. I went to the doctors with 72 hours...they just stuck me on a course of antibiotics and expect me to sit tight for nearly 2 weeks. What should I do?

[HotRodMike]

My medical history is pretty clean. Other than mild asthma and passing a stone once.. I have had no real medical issues, no surgeries, nothing really. My B.P was 122/78, H.R was 78, im 5' 10" and I weigh 220 lbs (that might sound heavy but I was a bodybuilder for many years, owned a gym, etc..) im not 220 lbs with a 44 inch waits or anything like that...waist was 35 last time I checked. Ride bikes daily, swim 5 times a week, I do resistance exercise 4 times a week and I eat well. As of today I have been on Antibiotics for 3 days and the lump still hasn't gone down, hasn't gone up either, seems fairly solid. Just worried. If they need to drin it, I hope its not painful. Im not sleeping well worrying about this.

[Christina Palmer, M.D.]

I understand your concern -- it can be very scary to find a growing lump in your armpit. However there are many possible explanations for this besides cancer. It’s impossible to know for sure without examining you in person and learning more about your medical history, but the most likely explanation is that this is an infection.

The most common cause of an infection would be a bacterial infection of a hair follicle. This could lead to a collection of pus (an abscess) under the skin. When this happens, oral antibiotics may not reach the infection and it may need to be drained. You could also have a viral infection leading to swollen lymph nodes in this area.  

You are right that it is very important to make sure that a growing and nonpainful lump is not cancer. If this lump does not go away or continues to grow, I would recommend that you return to your physician. If it looks like an abscess, they may be able to drain it to remove the infection. If it does not appear infectious, they may be able to ultrasound the lump and do a biopsy to get a diagnosis. Good luck!