I have a small painful lump on my right breast, that is now swelling. What should I do?

Breast Lumps. Breast lumps can be caused by infection, scar tissue, benign cysts, benign tumors and by cancerous tumors. There are other less common causes as well. You need to see your primary care physician to determine if mammography, breast ultrasound, breast biopsy or referral to a specialist is indicated.