Is having a small lump inside my breast a sign of breast cancer?

Many Possibilities: In my surgical practice, the most common cause of a well-defined breast lump is a cyst. This can easily be differentiated from a tumor by ultrasound or needle aspiration. If the lump is solid, it may be due to a benign tumor (ie, fibroadenoma) or a cancer; the only way to determine this is by tissue diagnosis, which can usually be done by needle-biopsy in the office or breast center.