Sometimes the comfortable choice is to wait and hope a problem goes away. Choosing courage over comfort often means getting it checked sooner.
This photo shows a woman sitting on an exam table, looking down at a swollen red lump on the back of her upper arm, just below the shoulder.
The lump is most likely an inflamed epidermoid cyst. The upper arm and shoulder are common places for them because the skin there has many follicles and gets rubbed by clothing.
These cysts form when a follicle is blocked and keratin collects in a small sac under the skin. The sac can stay small for a long time before it suddenly grows.
When it becomes inflamed, the skin turns tight, shiny and red, and the area can throb or ache when the arm is moved or when lying on that side.
