Cancer kills: Nearly 1.7 million people will receive a cancer diagnosis in 2017, and more than 600,000 people will die from it, according to a report from the American Cancer Society (ACS).

And the picture seems especially dire for men. For all types of cancers combined, cancer rates are 20 percent higher in men than women—and they are 40 percent more likely to die from it, too. So it’s no surprise that cancer ranks as the second most-common killer of men.

The even scarier part? Many of the leading cancer killers have no clearcut symptoms in their earliest stages. And that’s one instance where ignorance definitely isn’t bliss: Hard-to-spot cancers—whether preventive screenings aren’t available yet or you don’t recognize the symptoms as something serious enough to get checked out—can lead to a delay in diagnosis and treatment, which can reduce your chances of successfully beating it.

So for this National Men’s Health Week—a nationwide initiative which aims to increase awareness of preventable health issues, early detection, and treatment for diseases facing men—we’re making it our mission to shine a light on these hard-to-spot cancers.

Read on to find how they might take hold in your body before you even realize it, and what you can do about them before it’s too late.

WHY LUNG CANCER CAN BE HARD TO DETECT

Even though prostate cancer may be more common, lung cancer is by far the leading cause of cancer death in men. Only 16 percent of lung cancer cases are diagnosed at an early stage, according to the American Lung Association. Once the disease spreads and becomes more aggressive, only 4 percent of people survive at least five years.

Why it’s hard to detect: Most people associate lung cancer with smoking, but that doesn’t paint the whole picture, says David Ross Camidge, M.D., Ph.D., professor of medical oncology and lung cancer researcher at the University of Colorado Cancer Center.

While smoking is linked to the majority of lung cancer cases, the disease still strikes people who have never even touched a cigarette, he explains.

In most other cases, blame radon, a natural gas that you can’t see or smell. Radon is the second leading cause of lung cancer in the U.S.—and about 1 in 15 homes have high radon levels, according to the CDC. 

Plus, you might not even realize you have lung cancer until it’s already advanced to a more deadly stage: “Your lungs are mostly air, so you can actually grow a fairly decent sized mass without even noticing it,” says Dr. Camidge. “By the time you get symptoms, the cancer may have already spread.” These symptoms include a constant cough, shortness of breath, and unexplained weight loss.

But the U.S. Preventive Service Task Force has pretty narrow guidelines for who it recommends receive CT scans for lung cancer screening: those who smoked a pack of cigarettes a day for at least 30 years, are either still smoking or have quit within the last 15 years, and are aged in their 50s through 70s.

“So if you’re a guy in your 30s and you’ve never smoked, you’re never going to qualify for a screening test,” says Dr. Camidge.

What you can do: Skip the stereotypes. Regardless of whether you’re a smoker or not, don’t ignore the telltale signs of lung cancer listed above when they do appear.

Many doctors will hear that you have a cough, have never been a smoker, and automatically assume that it can’t be lung cancer, says Dr. Camidge. So they’ll usually treat you for less serious conditions that share common symptoms, like asthma or bronchitis. But if your cough persists for a couple of months, you should talk to your doctor about your options for a test, especially if you cough up blood.

WHY COLORECTAL CANCER CAN BE HARD TO DETECT

Colorectal cancer is the second leading cause of cancer death in men in the United States, according to the ACS.

While the majority of colorectal cases affect men over 50, the disease is quickly on the rise in young people, too. People born in 1990 have double the risk of colon cancer and quadruple the risk of rectal cancer than people born in 1950, when colorectal cancer risk was at its lowest, according to a study from the ACS.

Why it’s hard to detect: While colorectal cancer comes with its fair share of symptoms, they don’t typically appear in its earliest stages, when the cancer is most likely to be cured, says William Grady, M.D., a clinical researcher who specializes in colon cancer prevention at the Fred Hutchinson Cancer Research Center in Seattle.

“You won’t know if you have an early colorectal cancer. The only time you’ll know is when it’s much more advanced. Even then, the symptoms are so nonspecific that it’s hard to know what they mean,” he adds. This means you might mistake common symptoms—which include abdominal cramping, blood in your stool, and a persistent, unexplained change in your bowel habits, such as constipation or diarrhea—for some other type of stomach or digestion issue instead. 

That’s why it’s vital to get yourself checked through regular screening, since pre-cancerous growths can be removed before they develop into cancer—and before they start causing those symptoms.

Almost all colorectal cancers start out as a benign colon polyp, a clump of cells that forms on the lining of your colon or rectum, says Dr. Grady. Only 1 in 10 polyps will ever become a cancer if they do, and it usually takes about 10 to 15 years for the cancer to form. Colonoscopies are the most powerful way to find and remove a polyp early.

But if you don’t get yourself checked, there’s usually no outward sign of colorectal cancer until it advances, and you start experiencing its red-flag symptoms, like the ones mentioned above.

What you can do: Ask your doctor about screenings. Only a little more than half of people who should get tested for colorectal cancer do so, according to the ACS.

Most guys should start getting regular colonoscopies at the age of 50. But if you have a first-degree family member that suffered from the disease, you should start screenings at 40, or 10 years younger than they were when they were first diagnosed, the American College of Gastroenterology recommends.

These colonoscopies can be a lifesaver: 9 out 10 people who are diagnosed with colon cancer early are cured, says Dr. Grady. For those who are diagnosed late, after the cancer has already outside of the bowels to other organs like the liver or lungs, only 1 in 20 are cured. (Here are six ways you can prevent colon cancer.)

WHY PANCREATIC CANCER CAN BE HARD TO DETECT

The ACS predicts that 27,970 men will be diagnosed with pancreatic cancer in 2017—compare that to the 116,990 men that will be diagnosed with lung cancer. Still, while pancreatic cancer accounts for just three percent of all cancers, it makes up about 7 percent of all cancer deaths.

One reason it’s overrepresented in the death column? The disease is one of the most insidious ones out there: “We don’t have any way to screen for pancreatic cancer, and symptoms don’t develop until it’s usually not curable, so almost everyone who gets pancreatic cancer dies from it,” says Dr. Grady.

Why it’s hard to detect: Abdominal or back pain, weight loss, lack of appetite, nausea, and even blood clots are pretty nonspecific symptoms of pancreatic cancer that could be attributed to lots of other things. The cancer usually has to spread to your liver before you develop a telltale sign that something’s really not right: jaundice, which causes your skin and eyes to yellow.

The structure and setup of your organs is part of the reason. Your GI tract is basically a series of tubes and organs with different layers, including your pancreas, says Dr. Grady. The layers around some areas, like your colon, are quite thick. Thicker layers allow cancers more time to grow before they spread to other organs, potentially boosting your doctor’s chances of finding it in time to treat it before it becomes aggressive.

But your pancreas is different—its outer layers are pretty thin. That means the cancer can quickly spread outside the pancreas. “We think the problem is that by the time you develop symptoms, the cancer has almost always spread outside the organ into different regions,” says Dr. Grady.

Plus, your pancreas is located deep within your body, so your doctor can’t see or feel early tumors during routine checkups, according to the ACS.

What you can do: While researchers are putting in a lot of effort to come up with better early-detection tests, nothing like that is currently available for most people, says Dr. Grady. Like colon cancer polyps, there are precancerous lesions on your pancreas that may go on to become cancer, but more research needs to be done to know for sure, he says.

So prevention is key. The best thing you can do is to minimize your risk, says Dr. Grady. Smokers are twice as likely to develop pancreatic cancer than people who have never smoked, according to the ACS. (Here's the best way to quit smoking forever.) And since obese people are 20 percent more likely to develop pancreatic cancer, maintaining a healthy weight is crucial, too.

WHY MELANOMA CAN BE HARD TO DETECT

While melanoma accounts for only about 1 percent of skin cancers, it causes a majority of skin cancer deaths, according to the ACS.

And it’s on the rise. Melanoma rates have doubled in the last three decades, according to the Centers for Disease Control and Prevention (CDC)—and guys are particularly at risk. Men who have developed stage-four melanoma are more likely to die from it than women, possibly due to immune system differences, says Tara Gangadhar, M.D., assistant professor of hematology oncology at the University of Pennsylvania’s Perelman School of Medicine.

Why it’s hard to detect: It’s not exactly easy to eyeball the difference between a harmless spot on your skin and a cancerous mole. One big reason? You might not be aware that a dark brown mole isn’t the only sign to look out for, says Dr. Gangadhar.

Some melanomas are colorless, flesh-colored, or even red and pink—meaning you might brush it off as a pimple, wart, or not even notice it at all, she says. Plus, even if you do find a suspicious mark, hectic schedules can get in the way, so you might put off getting it looked at while the cancer is in its earliest stages.

But ignoring the warning signs can be fatal: Even after melanoma has been surgically removed from your skin, it can come back and spread to other organs like your lungs, liver, or brain, making it much harder to cure, explains Dr. Gagadhar. Other skin cancers like squamous cell and basal cell carcinomas rarely recur or spread at the same rate that melanoma does.

What you can do: Scan your skin—even if you slather on the sunscreen. You’re still at higher risk for developing melanoma if you experienced sunburns as a kid, says Dr. Gangadhar.

So if you notice any changing lesion on your skin, get it looked at by your doctor or dermatologist, says Dr. Gangadhar. Changes in the shape, color, or border of your moles should all raise a red flag—but cancerous moles can bleed, grow rapidly, and become itchy, too. (These pictures show you exactly what skin cancer looks like.)

WHY LIVER CANCER CAN BE HARD TO DETECT

Liver cancer is the fast growing cause of cancer deaths in the U.S., according to a new ACS report published in CA: A Cancer Journal for Clinicians. In fact, liver cancer deaths have doubled since 1980.

Only 1 in 5 people will survive five years after they’re diagnosed, the report found. What’s more, the disease is more common in men—the ACS predicts 29,200 guys will be diagnosed with the disease in 2017.

Why it’s hard to detect: There hasn’t been a ton of progress in figuring out how to effectively detect liver cancer at an earlier stage before it spreads, says Kim Miller, M.P.H., an epidemiologist at the ACS. Serious symptoms—like loss of appetite, feeling very full after a small meal, abdominal pain, and jaundice—don’t really appear until the cancer has already become difficult to treat.

Plus, your ribcage covers most of your liver, so it’s not easy for you or your doctor to feel a tumor there if you develop one, she says.

What you can do: Know your risk. A big reason liver cancer deaths are on the rise is because of the hepatitis C epidemic among Baby Boomers, or people who were born between 1945 and 1965, says Miller. Hepatitis C is the leading cause of liver cancer and liver transplants, since it can lead to liver damage and cirrhosis, scarring and inflammation of the liver, according to the CDC.

That’s why the CDC recommends getting blood tests done to detect if you’ve ever been infected with the hepatitis C virus. Successful treatments can completely eliminate the virus from the body, minimizing your risk of developing liver cancer.

Even if you’re not among the Baby Boomer generation, getting yourself vaccinated against the hepatitis B infection can help keep you protected too, since it can also cause liver damage.

And if you are at high risk—meaning you have chronic viral hepatitis, cirrhosis, or metabolic disorders like excess bodyweight and type-2 diabetes—there are some physicians out there who offer screening tests, like ultrasounds and CT scans. But there isn’t yet data out there to confirm the effectiveness of them, says Miller.

This article first appeared on Men's Health.