If the cells come from a stage leading to cancer where basal cells have stopped differentiating, you will see a bunch of round cells. A computer builds up a 3-D image point by point. In MRI, a magnetic field is imposed on the tissue and things like swelling can be detected. Tissue around a tumor could be swollen after being injured by the tumor. Unfortunately, MRI is not that useful for lung cancer, although it is useful for brain cancer.
Local anesthetic is used.
This way a physician can see the passageways and see if there is a mass of cancer tissue. A small knife can be inserted in the same tube which can cut out any abnormal tissue. The most invasive diagnostic procedure is surgically opening the chest cavity and looking at the lungs directly. The lung epithelium has columnar cells and goblet cells. Basal cells, at the lowest level, divide to produce new epithelial cells that will become either columnar or goblet cells.