The appearance of a shadow on the lung may be benign tumors , cancer, or it may not mean anything at all as it doesn't not necessarily mean cancer, because there are many reasons for the appearance of a lung shadow, as follows:
Pneumonia
Respiratory illnesses
infections
an overlap of completely normal structures
Normal glands inside the lung
Fluid in the lung's air sacs.
In general you should have a CT scan to remove doubt with certainty.