Bra fitting can be a mine field and there is plenty of misinformation available on the world wide web. One thing is a certainty though and that's your anatomy.
Got armpit bulge? The first thing we recommend doing is making sure you are wearing a cup size that is large enough to encase your entire breast. The center gore should tack to the chest wall and the underwire should sit comfortably at the back of your breast, under the arm. If the underwire is too narrow for your breasts it may squish your breast tissue backwards creating what is often called *back fat*. Note to self: back fat is normal, we are not made of stone!
Do the Scoop and Swoop. Reach into the cup and gently lift all of your breast tissue towards your middle and upwards, making sure that the underwire sits directly underneath the breast.
Are you bulging? If after doing the Scoop...scoop and swoop...scoop and swoop you have breast tissue spilling over the top or sides of the cup it's time to try the next size up.
BUT
I have a tail? Many women will have a small amount of fleshy tissue left sitting outside of the cup and this doesn't indicate a poor fit. This is normal anatomy and is called your Tail of Spence.
Wikipedia tells us that the Tail of Spence is an extension of the tissue of the breast that extends into the axilla. It is named after Scottish surgeon James Spence ( thank you Scotland!) and contains 2 lymph nodes. Now that we've got the technical bit out of the way....
Embrace it! Trying to squeeze your Tail of Spence into the bra cup by increasing your cup size will result in a poor, uncomfortable fit and a gaping cup. Some full cup styles will encase this fleshy tissue but unless you find the strap sitting on your Tail of Spence uncomfortable there is absolutely no reason to worry.
I've always wanted to be a feline, and now that I have a tail I'm going to channel my inner wild cat. Purr....