<s>[INST] Hello doctor, I had a smoking history of three years. Three months back there were a few blood drops were there in the phlegm while clearing the throat. Out of curiosity I had few like chest x-ray, chest CT scan with contrast (lymph nodes were there but in CT reports it was written like no significant lymph were seen), and PFT. All tests are normal. I have a few questions which are striking me. What is the accuracy of chest CT? Do this really rule out the probability of something like lung cancer? There is no weight loss but some chest congestion is there. I am feeling difficult to breathe and I am having heavy breathing. What can be this if my PFT is clear? Can this be lung cancer? Do I need to test further? Please suggest. [/INST] Hello. After going through your case, I do not think there is something to worry about the possibility of lung cancer as it can be just a smoker's bronchitis. As you said, you do not have any symptoms at present and all the tests including x-ray CT (computed tomography) and PFT (pulmonary function test) are within the normal range, there is nothing to worry about. The chest congestion blood flecks in phlegm and breathing difficulty you suffer are because of underlying bronchitis due to smoking. As far as investigations like CT scan and x-ray are concerned, they are very accurate in finding out the underlying abnormality. So no need to doubt even x-ray and CT are normal. The most important thing now is how to prevent further damage to the lungs and restore normal breathing. For that, I strongly recommend you stop smoking right now. Smoking cessation is the only way to improve your lung health. You can take the help of your family doctor in smoking cessation. If you find it difficult, he may prescribe you some medicine. I would advise you to do some exercises on a daily basis or gym as per your schedule as it would boost your stamina and exercise tolerance also. So all the best and do not be anxious about lung cancer but stay determined to quit smoking. Smoking. Bronchitis. Quit smoking, Nicotine chewing gum. </s>