Pancoast tumors get their name from Dr. Henry Pancoast, who was the first radiologist to describe them.
So to be clear, these tumors are classified based on their location in the lung apices - the tops of the lungs - rather than on the type of lung cancer they emerge from.
The reason that Pancoast tumors are given special consideration is that this location allows them to interfere with nerves and blood vessels, which leads to problems that are unique from tumors in other locations.
Lung tumors are divided into small cell and non-small cell cancers based on the way they look under a microscope and how they behave.
Generally speaking, small cell lung tumors are made up of small cells which divide rapidly and spread quickly, and non-small cell lung cancers, which should probably be called large cell lung cancers, have large cells that divide and spread slowly.
As it turns out, the majority of Pancoast tumors are non-small cell lung tumors, but a few are small cell lung tumors.
Most of the time, the signs and symptoms of Pancoast tumors result from the tumor creating local inflammation and swelling and pushing up against nearby nerves or blood vessels – which disrupts their function; a phenomenon known as mass effect.
In some instances, there is tumor invasion, which is when tumor cells penetrate and grow directly into surrounding structures.
Now, at the first thoracic nerve root or T1, you’ve got sympathetic nerves that supply the head, neck and eyes.
This point is super close to the lung apices and so susceptible to compression or even invasion from a nearby Pancoast tumor.
Normally, these sympathetic nerves help to dilate the pupil, raise the eyelid, and help stimulate the sweat glands.
If a pancoast tumor pushes on or invades these sympathetic nerves, it can cause miosis - a small or constricted pupil, ptosis - a droopy eyelid, and anhidrosis - a failure to sweat, all on the ipsilateral, or same side, of the face as the nerve.
Together this triad of symptoms is called Horner’s syndrome, and happens on the same side of the face as the nerves.
If the tumor cells invade or grow into the brachial plexus - which is a collection of nerves that supply the shoulder and arm, individuals can get shoulder pain and weakness.