Calcified nodules on chest X-ray is a common finding that is most commonly benign and caused by an old healed infection. On chest X-ray this will be a white nodule that has calcium deposit and looks whiter, similar to bone. Determining whether a nodule is calcified can be difficult on chest X-ray at times, particularly if the nodule is small or overlies a bone or blood vessel.
By far, the most common cause is an old healed infection, possibly fungal or tuberculous, that you didn’t even know you had. This is often associated with calcified lymph nodes or more then one calcified nodule, also called a granuloma. A healed varicella pneumonia will be associated with multiple small calcified nodules throughout the lungs on chest X-ray.
A benign tumor called a hamartoma can be calcified and lead to this appearance on chest X-ray. Some occupational exposure such as silicosis or the type that coal workers get can lead to calcified nodules on chest X-ray. Disorders of metabolism such as from kidney failure or calcium therapy can lead to calcified nodules on chest X-ray. A narrowing of the mitral valve of the heart can lead to small calcified nodules.
Some rare more concerning abnormalities are metastatic tumors that calcify such as bone tumors called osteosarcoma or medullary thyroid carcinoma. In these cases, the primary tumor will often be known and suspicion will be high for spread to the lungs. Some primary tumors of the lung can have calcifications as well. The pattern of calcification in the nodule will be important to determine the suspicion.
In cases which are not clear, a chest CT will provide a much more detailed view. This will determine whether a calcified nodule on chest X-ray is truly calcified, and whether there are any suspicious features that require further testing. The clinical history your doctor takes will also be very important in providing the best diagnosis.