Three cases of primary lung cancer undetected by an annual checkup

An annual check by chest roentgenogram is very important for the early detection of lung cancer. We present three cases of primary lung cancer which were not detected by the double check system or previous examination. The three patients visited our hospital for evaluation of an ill-defined opacity in the upper lobe of the lung. In the three cases, no abnormality had been reported in the previous year's annual chest X-ray, and we concurred in the decisions. The correct diagnoses of the three cases were well or poorly differentiated adenocarcinoma, and were still amenable for surgical therapy. A poorly defined tumor in this region is very difficult to detect because of superimposed opacities of other anatomical structures. When a questionable shadow in this region is found but without the typical radiological features of lung cancer, it is important to search for indirect indications of adenocarcinoma. These may include fibrotic changes and absence of inflammation. In our cases, the increased number of normal-size bronchi penetrating the ill-defined tumor, seem to have diagnostic significance.