Mom just diagnosed - 9cm dcis reoccurrence

Hi. My mom is 72 and had dcis 2 years ago and had a lumpectomy and radiation. Last week they did an MRI and found a 9cm mass in her duct. Same side as first diagnosis. Her doctor said it's contained in the duct and can't schedule her mastectomy for 4 weeks!!! My mom told her she had some shoulder pain and breast pain over the past week or two and is worried it has spread. I think 4 weeks is a long time to wait for a mastectomy for a 9cm mass. They said they will test the nodes when she has he surgery to see if it has spread. Can anyone tell me their thoughts on this? I am wondering why they can't give her a pet scan to see if it has spread and then if it has they should do the surgery sooner. I am very worried. Any info would be appreciated. Thanks.

Valerie