What can I do about this very painful LARGE armpit fat/back fat? (photo)

Thank you for your pictures and questions. I am going to disagree with a lot of other surgeons on here who are going to tell you that you need liposuction, etc. This is called aberrant axillary breast tissue. It is where during development, some of the glandular breast tissue gets held up in the axillary area instead of descending into the chest. As you develop, this area can swell and get tender and can even get larger during your cycle. I have even had patients who also had an accessory nipple in the area or when they became pregnant, the area swelled with milk production. This problem needs to be addressed with direct excision and removal of the breast tissue and it needs to be sent to pathology for evaluation. This should be covered by insurance. You need to talk to your regular doctor about a referral to a a plastic surgeon who takes insurance to deal with this type of problem. Hope this helps!

For best results removing fat in this area and body shaping, I recommend a hi definition procedure like VASER liposuction. I use VASER HI DEF with ThermiRF and fat grafting to get the most fat removal, skin tightening, contour and definition. This combination will give you the most toned result. I recommend getting a formal evaluation with a hi definition physique expert. Best, Dr. Emer

You look to have axillary breast tissue.  If soft it could be treated with liposuction but, as most are fibrous, surgical excision is usually required.
In view of the pain, it may be something that can be treated by medical insurance.

The area is called the Axillary Tail of Spence and is quite common in many women and can effectively be removed with surgery in many cases with liposuction or direct excision.  Dr Corbin

This fat pad is actually an extension of your breast.  This tissue can be very fibrous and sometimes lipo just does not work well.  Also with large axillary fat pads, lipo can result in unsightly skin sagging.  In your case, I think the best result will likely be obtained with actually excision of the area.  The resultant scar is usually very acceptable and this can often be done under a local anesthetic to keep the cost down.