Is infiltrate a sign of lung cancer?

Not necessarily: An infiltrate seen on a cxr or ct scan can be cancer or infection (pneumonia) or inflammation. It is by no means definitive for cancer. If it looks suspecious enough on the scan, the next steps are further imaging or direct biopsy of the abnormality.

See below: Not necessarily; most often infiltrative findings on x rays are non cancerous. The need for follow up and further work up depends on the clinical scenario and needs to be decided by your doctor.