A lung shadow may be a mass, or it may be a patchy shadow or lung nodule caused by inflammation. A lung shadow is an imaging descriptor that refers to the presence of an area of high density within the lung parenchyma on chest radiograph or CT, often appearing as a patchy shadow, nodule, or mass. A lung mass is usually a solid mass larger than 3 centimeters in diameter and is most commonly seen in diseases such as malignant tumors, inflammatory granulomas, and primary lung cancer. A diameter of less than 3 cm is usually referred to as a pulmonary nodule and is clinically common in inflammation, infection, tumors, and dust inhalation. Patchy shadows are overwhelmingly caused by infectious lung diseases or immune system diseases, such as pneumonia, bronchiectasis, tuberculosis, pulmonary aspergillosis, rheumatic pneumonia, connective tissue disease and other diseases. If you find lung shadows, it is recommended that you go to a regular hospital as soon as possible for further diagnosis and treatment, so as to avoid delaying your condition.