Its hard to say, but if it is a move-able lump then it is most likely benign, but if it is a hard lump that you can't move from side to side, then it could be cancerous. Just go to the dr. And have it checked and removed, to be safe.
Breast Lesion 1 Cm, Solid, Stable Peripheral Calcifications, Is This Indicative Of Breast Cancer Or Benign Cyst?