See as per your history It's Either a pad of fat Or Breast tissue To rule out Examination has to be done Do one USG And if only nessesary Or u getting consmatic issues than go for treatment

Its called Tail of Axilla... Its just a fat tissue in armpit usually present in both armpit.. Its not disease.. Its not cancer.. It can not turn into any disease.. No treatment required unless you want to do it for cosmetic reasons or its painful while movements.. It can be reduced only by surgery..no other medicines will reduce it

Kindly get an ultrasound done Nothing to worry whether it's lipoma or axillary tail If bothering much consult Surgeon for further management

Fat in armpit can be lipoma or axillary tail of breast.