Thanu, your mother-in-law's diagnosis is confusing - she can't have both non-invasive and infiltrating cancer, I don't believe. I'll assume it's IDC, and IS invasive. That said, her pneumonia is probably just that - pneumonia. Once she's recovered, I'd be sure to have her ask her oncologist to look at her lung scans, however, and possibly take some more, to make sure nothing is showing. Breast cancer can indeed metastasize to the lungs, so you need to be aware of that- don't worry, just be aware and watchful, OK? Good luck - PJH