Here’s a surprise from the nation’s number one cancer killer: It’s not just smokers who get lung cancer. In fact, as many as 1 in 5 Americans who die from this disease never used tobacco, says Catherine Ann Shu, M.D., clinical director of the Thoracic Medical Oncology Service at New York-Presbyterian/Columbia University Irving Medical Center in Manhattan.
Know what else? About a quarter of people with lung cancer are diagnosed by chance, after a chest x-ray or CT scan for something else entirely. The disease is sneaky that way, and it can show up in some confusing and cryptic ways.

The most common symptom of lung cancer is that “people don’t actually have any symptoms!” explains Nathan Pennell, M.D., Ph.D., a medical oncologist at Cleveland Clinic’s Taussig Cancer Center in Ohio. Given that, he says your best bet is to stay alert to “anything that just doesn’t go away when it should.” If any of the following symptoms linger longer than a month or so without an obvious explanation, alert the doctor, he says. Most of the time it won’t be cancer. “It will be normal stuff!” he says. But awareness pays: Lung cancer is sometimes curable when caught early. Here's what to watch for.

1. A Persistent Cough
This symptom is what most people relate to lung cancer, says Dr. Shu. "If you have a chronic cough, such as smoker's cough, and certainly, if you cough up blood or phlegm that’s in any way reddish or pink, see your doctor,” she says.
Most of the time a cough is happening for understandable reasons, such as a cold, says Dr. Pennell. It’s when it doesn’t ease up that you should snap to attention. “The average time a cough lasts after a virus is three weeks,” he explains. Hacking away for much longer than that? You know what to do.

2. Wheezing
If your airways are narrowed for some reason, you may hear a whistling or whining sound when you exhale, says Dr. Pennell. The symptom can be caused by problems such as asthma, emphysema, as well as lung cancer (the wheezing may result from air pushing past a tumor that's pressing on the airway). “This sound concerns people, because you usually don’t hear yourself when you breathe,” he says. On the other hand, a lot of long-time smokers are so used to wheezing that it stops setting off alarm bells. Remember: Wheezing isn’t normal, so get it checked out.

3. Shortness of Breath
It can be disconcerting to find yourself huffing and puffing when you're used to whizzing around without a second thought. “Shortness of breath can indicate a number of different things, from emphysema to pneumonia or even a blood clot,” explains Dr. Shu. When the culprit is lung cancer, the shortness of breath can come on in a stealthy way that you hardly notice...until one day you do.
"Everyone sort of knows how much exercise they can do before they have to stop and catch their breath,” says Dr. Pennell. So if the climb from the basement to the upstairs bedroom was easy in January but is now daunting in February, give the doctor a ring.

4. Loss of Weight (and Appetite)
Weight loss is a classic cancer-related sign, though not one necessarily specific to lung cancer, says Dr. Pennell. Cancer can cause you to lose weight as the illness burns up the body’s energy supply and alters the way you process energy from food. “Most very serious illnesses can cause this, as well as a loss of energy.” And since almost no one loses weight without trying, he adds, it’s a good idea to talk to your doctor if you’re dropping pounds without any apparent effort.
5. A Hoarse Voice
You may actually feel fine with this sneaky lung-cancer symptom and not notice anything odd other than that your voice is froggy. But when this occurs, it can be a sign that cancer has somehow compressed a nerve that innervates the vocal chords that connect to the lungs. “People who have a hoarse voice or laryngitis usually have it for a day or two, and then it goes away,” he says. “But if yours doesn’t come back to normal after a few days or a week, that’s much more concerning.”

6. Pneumonia
When lung infections like pneumonia keep coming back or don’t ever really go away, lung cancer’s worth putting on the list of conditions to get checked out, says Dr. Pennell. Pneumonia is an inflammation in the lungs caused by infection with a bacteria or virus. The cancer link is one reason doctors ask people to return for follow-up chest x-rays after diagnosing pneumonia—to make sure the pneumonia went away and that a tumor, which can be very small, isn’t lurking in the lungs. Many people with lung cancer are misdiagnosed for months or more because the illness can appear as pneumonia or even a cold or allergies, according to the American Lung Association.

7. Pain in the Ribs, Shoulder, or Back
Lungs have no nerve endings, so you can’t actually feel pain from a tumor there, explains Dr. Shu. “But a tumor could invade your chest wall or extend into the pleura (the lining of the lungs), both of which are sensitive to pain.” Some people develop a dull or aching discomfort around the rib cage, shoulder, lower back, or along the outside of the arm; white blood cells can pool in large numbers and damaging the bones. But unlike pain from an injury, lung-cancer pain doesn't go away. Instead, it tends to get worse over time, stresses Dr. Pennell.

8. Chest Pain
Since there can be so many serious reasons for having chest pain, including heart issues, it’s important to always get this problem checked out right away, says Dr. Pennell. It’s not common, but lung cancer can be a cause. The American Cancer Society describes lung cancer-related chest pain as “often worse with deep breathing, coughing, or laughing.” It may feel like a dull, persistent ache.
Unfortunately, feeling chest discomfort from cancer is “usually a sign that it’s become quite advanced,” explains Dr. Pennell, and already invaded the pleura or bones around your chest.

9. Finger Clubbing
This relatively rare but dramatic sign of lung cancer shows up in 15% of people diagnosed with lung cancer, according to the research in the journal Lung India.
Here's what it can look like: The nails take on the shape of the back of a spoon, and they may seem to practically float above the nail bed. Fingers may get red, swollen, and inflamed, and look like little sausages. No one know exactly what causes clubbing. It might be prompted by a drop in nutrient-rich oxygen circulating through the body, or it's possible that cancer activates certain substances in the bloodstream, causing the nail bed to thicken. Whatever the reason, if these changes happen to you, make that appointment.