Kirstie Alley, best known for playing Rebecca Howe in "Cheers," died this week at age 71, after a recent colon cancer battle.

"We are sad to inform you that our incredible, fierce and loving mother has passed away after a battle with cancer, only recently discovered," her children, True, 30, and Lillie Parker, 28, wrote on Twitter on Monday.

"As iconic as she was on screen, she was an even more amazing mother and grandmother."

KIRSTIE ALLEY DIED AFTER BATTLE WITH COLON CANCER, REP REVEALS

Alley's recent battle with colon cancer is raising more awareness about the disease. 

Here's a deeper look at it.

How many people have colon cancer?

"Every year, more than 100,000 people in the U.S. are diagnosed with colorectal cancer, and it is always sad when someone loses their life to this disease," said Dr. Cynthia Ko, professor of medicine (gastroenterology) at the University of Washington School of Medicine.

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Colorectal cancer is the third leading cause of cancer-related deaths in men and in women in the United States.

Kirstie Alley

Kirstie Alley during Showtime TCA Day at Universal Hilton in Los Angeles, California. Alley passed away this week of colon cancer at age 71.  (Jeff Kravitz/FilmMagic, Inc)

It also the second most lethal cancer among men and women, according to the American Cancer Society.

The society noted that 52,580 deaths are expected this year — but death rates of the cancer have been declining for the past several decades.

"Preventive screening is the most important thing that anyone can do to lower their risk of developing colorectal cancer."

That's likely in part because the cancer is found earlier in screening; polyps are discovered before they have an opportunity to develop into cancer and treatments have improved.

"Preventive screening is the most important thing that anyone can do to lower their risk of developing colorectal cancer or to detect it early when it is more treatable," Dr. Ko told Fox News Digital.

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"We encourage everyone to talk to their doctor about the most appropriate screening test for them," she also said.

What is colon cancer?

The gastrointestinal tract begins at the mouth, which is connected to several hollow organs — including the esophagus, stomach, small intestine and large intestine.

These organs create a "long, twisting tube from the mouth to the anus," according to the National Institute of Diabetes and Digestive and Kidney Diseases. 

The large intestine is composed of the cecum, colon, rectum, and anal canal, per the National Cancer Institute.

doctor patient

Not all polyps become cancer, but some can become cancer over time. This usually takes years, the American Cancer Society says on its website.  (iStock)

Colon cancer occurs when cells in the colon grow out of control, according to American Cancer Society’s website. 

The function of the colon is to absorb water and salt after food leaves the small intestine, which then becomes "waste matter" as it moves through the colon into the rectum.

The stool is stored in the rectum until it passes out of the body through the anus.

Colon cancer and rectal cancer are grouped together, often known as colorectal cancer, because the two organs share many of the same features.  

What are polyps?

"Most colorectal cancers start as a growth on the inner lining of the colon or rectum," according to the American Cancer Society’s website.

"These growths are called polyps."

Not all polyps become cancer, but some can become cancer over time. This usually takes years, the American Cancer Society notes on its website. 

Many people don’t have symptoms of cancer in the early stage of the disease.

Certain characteristics can increase the risk that a polyp contains cancer or increase the risk it can develop into cancer.

These include if a polyp is greater than 1 cm; if more than 3 polyps are found at one time during a colonoscopy; or if a condition known as dysplasia is present, according to the American Cancer Society.

doctor discussing topic with patient

If a polyp is not removed and a cancer forms inside of it, it can grow into blood vessels, then travel to surrounding lymph nodes or spread throughout the body.  (iStock)

Dysplasia is a pre-cancerous condition in which the cells look abnormal, but are not cancerous when the pathologist looks at the slides after a polyp is removed, the American Cancer Society added. 

If the polyp is not removed and a cancer forms inside of it, it can grow into blood vessels, then travel to surrounding lymph nodes or spread to distant parts of the body.

What are the signs and symptoms of colon cancer?

Many people don’t have symptoms of cancer in the early stage of the disease.

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Yet when symptoms do appear, they can vary depending on the size of cancer and the location of it in the large intestine, according to the Mayo Clinic.

Some symptoms may include a "persistent" change in bowel habits, rectal bleeding, blood in the stool, belly discomfort, unexplained weight loss and a feeling that the bowel can’t empty completely, Mayo Clinic added.

Who’s at risk for colon cancer?

Colon cancer can be diagnosed at any age, but most of those diagnosed are age 50 or older, per the Mayo Clinic.

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A past history of colorectal cancer or polyps; having certain inflammatory conditions such as ulcerative colitis or Crohn's disease; being of African American descent; having a family history of colon cancer; eating a diet low in fiber and high in fat; and having a sedentary lifestyle — all of these can increase the risk of colon cancer.

When does colon cancer screening start?

The starting age to screen for colon cancer recently has been reduced from age 50 to age 45 for most people.

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"The United States  Multi-Society Task Force (MSTF) on colorectal cancer  (CRC) has released updated screening recommendations, endorsing 45 as the age to start average-risk CRC screening," the American Gastroenterological Association noted on its website.

Patients should talk to their doctor or health care provider about what screening test is best for them.

One common screening method is a colonoscopy. In this procedure, a scope allows doctors to view the entire colon; if polyps are discovered, the doctor can remove them at the time of the procedure, according to the National Cancer Institute. 

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Other options include stools tests — such as Cologuard, which detects genetic changes in someone’s stool; or a FIT test (fecal immunochemical test), which detects blood that patients or doctors may not see with the naked eye but may suggest the presence of cancer, the institute added.

Patients should talk to their doctor or health care provider about what screening test is best for them.