@togerm, I agree with @lls8000 that it is not always possible to know that cause of one's cancer. In some (not so common) situations there are clear indicators like smoking, family genetics, mutations, environmental hazards, age, to name a few. More commonly, the cause of cancer is not simple to pinpoint.

Spots on the lungs are most commonly detected when a patient is getting imaging studies (x-ray, CT-scan, etc.) for another medical reason. One friend found his lung cancer when the x-ray technician noticed a spot on his lungs when examining the x-ray of his broken collarbone. One could say that the broken collarbone saved his life.

Lung cancer often doesn't cause noticeable symptoms until it is late stage. Thus finding the spot on your lung due to monitoring for COVID may be a silver lining.

@togerm, have you had a biopsy? Is it lung cancer or a different type of cancer?