Mentor saline implants got them placed in 1999 or 2000 - lumps in breast.

THe most common scenario that causes abnormal feelings such as these in old saline implants involves broken/leaking implants. Have them check out by a local Board Certified Plastic Surgeon. 

Any new lump in a breast should be examined whether someone has implants or not. Air bubbles are common early after surgery, but definitely should not be present this far down the road. Best of luck! 

After many years folds and the valve in breast saline implants can feel like lumps.  Please see your plastic surgeon  or primary care physician for an examination and person make sure there are no breast lumps or masses that need to be investigated.

Absolutely, have your breast checked.  You should not feel lumps in your breast because of implants.