Armpit fat or something more serious? (Photo)

Thank you for your pictures and excellent question.  The fat in this pre-pectoral area of the armpit is known as the Tail of Spence.  
When breast tissue comes in at puberty, it comes in like a comet having both a body and a tail.  This tail of breast tissue degenerates into breast fat early in the teenage years.  The Tail of Spence is mostly breast fat, but some actual breast tissue or gland remains for many women into their adult life.  Any breast tissue in the body can become cancerous.  The danger in the Tail of Spence is that some patients and physicians forget, in the monthly or yearly exams, to check this area for lumps.  The fact that you have a larger breast on the right side may mean that larger Tail of Spence on the same side would not be unusual.  
All the above being said, I highly recommend you see a physician to have this area checked by a professional to see if any of this tissue feels questionable.  Many plastic surgeons liposuction this area at the same time as doing a breast enhancement surgery.  Debulking this area of fat makes any discovery of unusual lumps much easier.  

this can be improved witth liposuciton and internal heating, If there is alot of loose skin It may need to be surgically removed. I would consult with us to go over what is best. see link for homonal optimizatoin and weight loss which helps enhance the results of any surgical procedure. Dr. Emer.

Dear olive101,
it is hard to tell for sure without an examination. If you are concerned, I would suggest you to get an examination. Only after a thorough examination you will get more information and recommendations. In most cases it is either fat tissue or accessory glandular tissue. 
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

This issue may be resolved using high defintion VASER liposuction. The Gold Standard for superior liposuction results requires use of the advanced technology of ultrasound assisted VASER liposuction. As an official trainer of VASER liposuction, I perform full body liposuction cases every week. VASER liposuction has been the only modality that has consistently resulted in outstanding liposuction outcomes. VASER liposuction ensures a smooth contour regardless of degree of excess fat by virtue of being able to remove any and all remaining fat comprehensively and uniformly. If skin redundancy is observed, Renuvion technology can be simultaneously applied to tighten your skin to optimize your overall contour outcome. A Skype or FaceTime consultation with a VASER specialist will help you get an accurate recommendation and pricing.
Respectfully, 
Arian Mowlavi MD, FACS
Realself 100 Hall of Fame Inductee

The fullness in your armpits including the side that’s larger than the other is a combination of breast tissue and fat.
Unless there’s something unusual going on other than having this we don’t need to worry about it.
It tends to be fairly soft tissue and responds very well to Liposuction.
The area tends to also have a component of skin laxity because of the range of motion of the shoulder and the fullness may stretch the shin as well. Most likely the bus action is efficient but on some people skin excision in combination is a better choice.
Probably Liposuction alone is a good option for you.
If you have children in the future you can expect the area to engorge  as your breasts  do.
Best, 
Mats Hagstrom MD