Healthy lungs are pink sponge-like organs made up of tiny blood vessels (capillaries and veins) and air sacs (alveoli) which deliver oxygen to the body during breathing. A lung (pulmonary) nodule is a small oval or round growth in the lung, often referred to as a "spot on the lung" or "coin lesion" as seen on a chest-x-ray. Lung nodules may be either benign (scarring from prior infection, or a benign tumor) or malignant (a primary lung cancer arising in the lung, or a secondary focus of malignancy that has spread or metastasized to the lung from another organ). More than half of solitary pulmonary nodules are benign, but conversely, a substantial number are malignant.
Causes of Lung (pulmonary) Nodules
Benign lung nodules can be caused by a variety of factors including the following:
- an enlarged lymph node in the lung
- scarring in the lung caused by a prior infection (fungus, pneumonia, or tuberculosis and sarcoidosis which cause the formation of a unique type of scar called a granuloma
- scarring in the lung due to inhaling highly irritating substances such asbestos, coal dust, or tobacco smoke
- a clump of abnormal blood vessels (angioma)
The likelihood that a pulmonary nodule may be due to cancer is influenced by a number of variables include the patient’s age and medical history; genetic factors; the size and shape of the nodule(s); a history of cigarette smoking either current or in the past; past exposure to substances harmful to the lungs (including asbestos, coal dust, and certain chemicals); and whether the nodule has grown in size on serial chest x-rays or CT scans or is getting smaller.
Symptoms of Lung (pulmonary) Nodules
A solitary lung nodule rarely causes symptoms and is discovered incidentally on a chest x-ray or CT scan obtained for other reasons.
Diagnosis of Lung (pulmonary) Nodules
Lung nodules are evaluated by chest x-rays, which show the interior of the chest cavity and computed tomography (CT scans), which produce a series of images of the inside of the body, taken from different angles and depths, to reveal a high level of detail.
To help determine if the lung nodule is malignant, a PET scan (positron emission tomography) may be obtained. Every living cell in the body uses glucose to function normally. Tumor cells are often metabolically active (growing faster than normal cells) and therefore taking up more glucose. With a PET scan, a small amount of radioactive glucose is injected into a vein. The scanner then revolves around the body, identifying areas where glucose uptake is the greatest, often areas of tumor or tumor spread. A pulmonary nodule which is very “hot” (taking up a large amount of glucose) may be due to malignancy diagnose but can also be caused by inflammation or infection.
A biopsy of the lung nodule to help determine whether the nodule is benign or malignant may before using CT guidance (fine needle aspiration) or through a bronchoscope, a camera inserted into the airway (navigation bronchoscopy).
At times, certain blood tests may be helpful in deciding if the nodule has been caused by an infection (like tuberculosis or pneumonia) or by inflammation.
Treatment of Lung (pulmonary) Nodules
Treatment options depend on the specific cause, size, and general appearance of the lung nodule. Nodules felt to be benign or caused by infection may be treated with antibiotics and/or observed with a repeat CT scan 8 weeks later to be certain the nodule is not growing larger.
When there is a concern that the nodules are cancerous, an operation may be required to prove if there is in fact a malignancy. If a primary lung cancer (originating in the lung) is discovered, a portion of the lung may need to be removed (wedge excision or lobectomy). This can usually be performed “minimally invasively” with video-assisted thoracic surgery (VATS), in which small instruments and a camera are inserted into the chest through several very small incisions.
The thoracic surgeon will discuss the diagnosis and possible treatment options with you and help you to determine the best course of treatment.
Take the Next Step
Contact the Thoracic Cancer Clinic at the University of Michigan to assemble a team of specialists and construct a plan of action.