CA15-3, undiagnosed lung 'infiltrates' - mammogram needed?

Dear Dr.
My mum has had a CA15-3 test which came out at 81. The doctor did this after an X-ray showed some shadows on her lung. She's 67.  A CT scan revealed nothing more and the doctor is currently evaluating the lung shadow, which he calls 'infiltrates' (not a lump or nodule). No diagnosis yet, but Dr. doesn't think it's cancerous. She is taking cortisol tablets for a week, then the doctor will reevaluate.
Given that the CA15-3 is elevated, should we do a mammogram also? I have heard that sometimes the CA15-3 elevates months before a breast cancer occurs, and CA15-3 is primarily an antigen test for breast cancer.
Should we wait for the mammogram (her last one was in August last year) or should we do it now to exclude breast cancer? My mum is very anxious (she also recently had colon polyps removed).
Thank you

[CCF-RN,MSN-rf]

Dear cnom:  A CA15-3 is a tumor marker that is sometimes (in some centers) used to track breast cancer (that has already been diagnosed).  It is not meant to be a screening tool.  In the setting where there is no known disease, the significance of an elevation is unknown.  You might discuss this with her doctor and if you are not comfortable, consider a second opinion.