Fibrous foci in the middle lobe of the lung refer to a description often seen on chest films and lung CT report cards, where fibrous foci are visible. If it is described on the CT of the lung, it is not a big problem. It is due to the scar left by the absorption of the lesion after the treatment of pneumonia or tuberculosis, which is more common in old tuberculosis. If there are also calcified foci, they are old foci left behind after regular anti-TB treatment, which is a sign of healed tuberculosis. Some patients have fibrous foci left behind due to incomplete absorption of pneumonia. If it is reported by chest X-ray, it is better to do CT of the lung again to make sure that it is indeed a fibrous foci in the middle lobe of the lung, because the images of chest X-ray some hide other lesions and are not accurate enough, so further examination is needed to make sure. Fibrous foci should not be confused with interstitial lesions of the lung, as there is a big difference between the two. Interstitial lesions can be associated with lattice-worked glassy shadows, thickened lobular septa, distended bronchial dilatation, or even cellular lung, which have a completely different pathogenesis. Do not be afraid to see a fibrous focus and think that you have interstitial lung disease, but always seek a doctor to identify it.