Medically reviewed by Doru Paul, MD Key Takeaways An armpit lump, also called axillary lump, can be a symptom of breast cancer.A healthcare provider should check any hard armpit lump that doesn't ...

A cyst is a sac or cavity that may be filled with pus, semi-solid material, or air. It doesn’t usually cause pain until it gets large. An abscess is a painful, red infection that’s filled with pus. A ...