A nodule is a spot that is a frequent finding on chest x rays. Nodules are spots that stand out from the dark lung and have a white appearance to the radiologist. A nodule can be any size up to about 3 cm. After that size its called a mass.
Lung nodules can have many causes, the most concerning of which is a small cancer. The radiologist can sometimes suggest a specific cause based on the appearance. If it is calcified, or real white and dense, sometimes a granuloma can be diagnosed which is benign. If the nodule is shaggy or has irregular edges, it becomes more concerning, particularly in someone who is a smoker. Sometimes nodules may simply be normal overlapping structures such as blood vessels or ribs.
A chest CT is often the next test that is suggested to take a closer look at the appearance of a lung nodule. Sometimes calcifications may be better appreciated and diagnosis of benign granuloma is made. Other times the radiologist may see fat and call it a benign tumor called a hamartoma. Other times a vascular malformation can be diagnosed if there are blood vessels feeding and draining it.
Sometimes it remains unclear and a follow up is recommended. If the nodule is under one centimeter, than follow up imaging is needed. There are well accepted published guidelines to follow. If the nodule is bigger than 1 cm then the radiologist may recommend another test such as PET scan or even biopsy.
Lung nodules can range from benign to cancerous. The smaller the size, especially under 1 cm, the more likely to be benign. Other features such as if it is smooth or irregular, your smoking history, and other features the radiologist sees will determine the next best step. Follow up imaging is a frequent recommendation, and in this case we are looking for stability and growth. When there is growth, then that becomes concerning. It is important to discuss this with your doctor as they know your history best and what your risk level is.