A recent study by CT found signs that lung adenocarcinoma can spread not only along the blood vessels but also along the airways. The so-called airway metastasis has implications for the staging, treatment, and prognosis of lung cancer, a study published by Eric Barnes et al. in the American Journal of Roentgenology. Li Tian, Department of Respiratory Medicine, Nanjing Chest Hospital In fact, there is increasing evidence that airway metastasis is more common than blood transmission. imaging features of CT can suggest the possibility of airway transmission. Blood vs. airway transmission Lung cancer is the most common cause of cancer death worldwide, with a 5-year survival rate of 6-18%, and lung adenocarcinoma accounts for up to 30% of lung cancer incidence. In a study done by Dr. AnandGaikwad and his colleagues from the University of Ottawa, Canada, a relevant article on airway metastasis is summarized to explain the possible pathogenic mechanisms, and imaging features and pathological characteristics of airway metastasis. Local venous spread can occur through pulmonary vein erosion and adjacent veins, but systemic dissemination is more common. The cancer cells generally metastasize to the most common locations of metastases, such as the liver, adrenal glands, bone, and cerebrospinal fluid, before reaching the heart and pulmonary arteries, and eventually both lungs. On CT, these pulmonary metastases metastasize through the circulation in a random distribution, with round nodules easily identified on CT and pathological examination. On the other hand, airway metastasis is defined as the discontinuous spread of cancer cells from the primary focus through the airway to the adjacent or distal lung parenchyma. CT features Signs of CT suggestive of airway metastasis include multiple lobular central nodules with blurred branches in the form of dendritic signs, usually with indistinct borders and visible ground glass shadows. In contrast, well-defined soft tissue nodular shadows are rarely seen in this setting. The nodules formed by airway dissemination have an aggregated distribution, and signs of nodule enlargement are seen in a series of imaging. In some cases, these nodules fuse to form cavity-containing cavities. When these metastases are distant from the primary focus, the nodules tend to form in the lower lobes of the lung. The above image shows the CT sign of airway dissemination of the tumor. Female, 49 years old, with no history of smoking. The image shows a primary lung adenocarcinoma in the middle lobe of the right lung with fusion of the lesions. A lobular central nodule (arrow) and cloudy alveoli are seen in a different bronchial branch away from the primary focus. Above, CT imaging of a 68-year-old man with an image showing primary pulmonary invasive mucinous adenocarcinoma in the right upper lobe of the lung. The poorly defined lobular central nodule (arrow) with a ground glass shadow is seen posteriorly. There is growing evidence in the literature that airway metastasis in lung adenocarcinoma is a previously unrecognized pattern of tumor progression with distinct pathologic and imaging features that are important for clinical management. The possibility of airway metastases should be considered in patients with lung adenocarcinoma who have persistent or progressively growing lobocentric nodules on CT, especially if these nodules are associated with an aggressive, mucinous, papillary or micropapillary staging. Airway metastases also need to be differentiated from other multiple lesions in the lung. Accurate diagnosis and appropriate treatment require multidisciplinary cooperation, including imaging, thoracic surgery, pathology and genetics. In cases where airway metastases are suspected, genetic analysis can provide strong evidence of monoclonality.