Getting investigated for new diagnosis in the other breast and living with advanced disease

Hi everyone I've just had routine scans along with mammogram in the left remaining breast. Mammogram results suggest DCIS. I'm getting a referral to breast specialist. But what happens under these circumstances ? Will they leave the breast intact or remove it? I'm worried about it going to my lymph nodes and having to fight it in my system. Has anyone else had this experience? I hate this waiting game. 

Regards, 

Melissa