<s>[INST] Hello doctor, I am a 72-year-old female with breast cancer. I underwent mastectomy twice for both the breasts. Right breast mastectomy was done with radiation and a few years later left breast mastectomy was done without radiation. A 4 mm size lesion on my left lung has been watched for two years with no changes. I have been having pain on the right side and in my arm and back. I also have shortness of breath. Recently chest x-ray showed increased interstitial markings on the right side. Should a CT scan be recommended to investigate this further? [/INST] Hello. Reading in between the lines of your query, your worry about having cancer for the third time stands out clearly, and very naturally so. The language of your query also reveals how scrupulous and conscientious you have been in terms of follow-up. It is a pleasure to be talking with such a sincere patient. Here, I will try to explain your present situation and alleviate your worries as best as I can. Since the left lung lesion has been unchanged for two years, it is unlikely to be related to your previous history of cancers. So, if it is still unchanged, it should not be a cause of worry. The "increased interstitial markings" may or may not represent lymphangitis carcinomatosa (LC) a type of lung cancer. Although this condition is mostly seen in addition to pre-existing cancer in the lungs or elsewhere, and there are also be some other findings on the chest x-ray, such as pleural effusion (collection of fluid around lungs), hilar lymph nodes (which appear as round masses in between the lungs). The chest x-ray may even be normal in 30 - 50% cases of lymphangitis carcinomatosa. However, increased interstitial markings may also represent a lot many other conditions unrelated to cancer and so, your treating doctor may want to first treat the condition like infection and go for the CT scan afterward, if the markings persist after treatment. Since the additional findings (effusion, lymph nodes, etc.) are not seen, and since you do not have a diagnosis of or complaints related to underlying cancer at present, I would say that you may first follow the treatment regimen planned by your treating doctor, and may go for the CT scan if the marking persist after that treatment. I hope this helps. </s>