What can cause large lumps in both of my breasts?

Breast masses. Breast lumps can be palpated anywhere. They can be in any quadrant, behind the nipple, or near the axillary region (arm pit). It can be normal breast tissue, fibrocystic, masses that are non-cancerous, benign masses like fibroadenomas or the dreaded cancer. Most cancers are located in the upper outer quadrant. See your physician for a history and physical. Diagnostic testing may be in order.