When many people go to the hospital for check-up, they will inadvertently find nodules in a certain part of the body, either in the lungs, or on the liver, or on the breast or thyroid, and then they will be shocked, and a cloud of suspicion will float over them: it can’t be a tumor, can it? This kind of worry is understandable and justified, because many tumors start as “nodules”. However, it must be noted that “nodule” is only a description of medical imaging, not a clinical diagnosis. Whether this abnormal finding in medical imaging examination is a tumor or will become a tumor requires clinicians to make a comprehensive analysis and judgment by combining with other clinical data. The condition of nodules may be different in each organ, how do we deal with them? Liver nodules The most common cause of liver nodules is hepatic fibrosis nodules formed by alcoholic liver disease and chronic viral hepatitis (Hepatitis B or Hepatitis C), the diameter of which usually ranges from 0.5-0.8cm and does not exceed 1.0cm. When there are more nodules, the hepatic lobules are destroyed and pseudo lobe is formed, which is known as cirrhosis. Schistosomal cirrhosis nodules are larger and can be more than 1.0-2.0cm in diameter. Because chronic hepatitis B and chronic hepatitis C are prone to hepatocellular carcinoma, the nodules present in these patients should be closely monitored, and ultrasound should be performed every 3-6 months. If ultrasound suggests that the diameter of the nodule is more than 1.0 cm, or if diffuse nodules cannot exclude hepatocellular carcinoma, then further magnetic resonance imaging (MRI) or CT examination should be performed, and the serum alpha-fetoprotein or abnormal prothrombin should be examined to provide more diagnostic information. Isolated nodules should be distinguished from hepatic hemangiomas and hepatic cysts. Thyroid nodules Most often detected by ultrasound. The incidence of thyroid nodules in adult females is around 30%, much higher than that in males. The reason for this is unclear, and whether it is endocrine-related deserves further study. Thyroid nodules can be categorized into multiple (more than 2) and single nodules, and we need to focus on single nodules because thyroid cancer is transformed from single nodules, and multiple nodules are usually not cancerous. If single thyroid nodule with diameter less than 0.8cm is found on physical examination, it should be closely and dynamically observed, and be examined by ultrasound once every 3 to 6 months. If there is no obvious growth, it suggests that the nodule is still in the benign stage and does not need any special treatment; once the diameter is more than 0.8cm, or even more than 1.0cm, then it needs to be examined by fine-needle puncture pathology, or be directly surgically excised in order to eliminate the future problems. Thyroxine (T3, T4) and thyrotropin-releasing hormone (TSH) should be detected at the same time of ultrasound examination in order to evaluate the effect on thyroid function. Breast Nodules Breast nodules may be lipomas, fibroids, cysts, calcified foci, or breast enlargements, but of course the most worrisome is breast cancer. Most breast nodules are detected by ultrasound. Nodules with a diameter of about 0.5cm can be clearly shown by ultrasound, and experienced ultrasound doctors can detect nodules with a diameter of at least 0.2cm. Experienced ultrasound doctors can detect nodules as small as 0.2cm in diameter. Large nodules can be touched with their own hands. If the ultrasound suggests that the diameter of the nodule is less than 0.5cm, it can be observed closely and dynamically, and the ultrasound can be done once every six months to reduce the local stimulation and to pay attention to the nipple with or without overflow, especially with or without bloody secretion, and the axilla with or without lymph node enlargement; if the ultrasound suggests that the diameter of the nodule is more than 0.5cm, then it can be done with the molybdenum target mammography (molybdenum target), which is more than 85% of the diagnostic specificity and sensitivity of the diagnosis. The specificity and sensitivity of molybdenum target for breast cancer diagnosis are above 85%. Lung nodules, mostly detected by radiology or CT examination, are round or round-like foci with clear boundaries less than 3cm in diameter, and those less than 2cm are also called lung nodules. The incidence of lung nodules has increased significantly in recent years, largely related to the improvement of imaging technology and diagnosis. Lung nodules can be benign or malignant, and 70% of lung nodules are benign, which can be caused by inflammatory lesions, fibrotic nodules, tuberculosis balls, and malformation tumors. Whether a nodule is benign or malignant should be analyzed based on the shape, density and size of the nodule. According to the density of the nodules, they can be categorized as: pure ground glass nodules, mixed ground glass nodules, and solid nodules. Pure ground-glass nodules are of particular concern because this density of nodules has the highest likelihood of presenting with lung cancer. The current consensus in the industry is that if the maximum diameter of ground glass nodule >1cm, CT follow-up is required once every 3 months, and if there is no change or increase in size, biopsy or surgical resection is recommended; if the maximum diameter of pure ground glass nodule ≦0.5cm, there is no need for further evaluation, and CT follow-up is required once a year; if the maximum diameter of 0.5cm﹤pure ground glass nodule≦1cm, CT follow-up is required once every 3 months, and there is no change in the diameter of pure ground glass nodule in the follow-up period of 3 years, the nodule can be roughly considered as benign. If there is no change after 3 months of follow-up, the nodule can be considered as benign. Low-dose CT is recommended for chest review.