Bras and the lymph nodes
I've noticed at times that the area beneath or at the side of my breasts have become tender, usually after wearing a bra (especially a sport bra) that's been pressing on the lymph there for too long. When the connection became clear I went out shopping for different types of bras. Mind you, I'd already stopped using the underwire type, but even without that added firm material of the underwire, the tension on the diaphragm and the lymph nodes had become too much. Sport bras are really tight usually, but there are some that give just enough support so the fluid and sensitive membranes can breathe. I found a few pregnancy bras that are so comfy and light, as well as some other minimal support types that don't have diagonal straps that strain the traps, but everyone is so different that each one would have to do a personal exploration on this one.
A very light stroking, or massage up from the elbow, into and through the armpit and across the chest to the sternum does wonders to help the lymph drain while it softens the muscles in the upper arm. Congestion can build there that may look like a tight, sore muscle or feel like heaviness in the arms, but it may be congestion in the lymph nodes there. You can also take the massage route from the armpit around and under the breasts then up the center of the chest up to the clavicle. After a few times you'll notice those areas aren't tender anymore. There are other experiences and conditions besides a tight bra that can congest the lymph, as it plays a major role in elimination, immune system support, circulation of fluids, and more. Illness, injury, allergies, infections, and emotional upsets or stresses can also inhibit the flow of the lymph. Understanding how to monitor some of the major spots of congestion for yourself can help this system play its optimal role of maintaining health and balance in your body.