8 Cancer Red Flags Your Doc Should Never Ignore

There are more than 200 kinds of cancer. How can doctors possibly be able to spot them all? Recently a team of researchers led by Dr. Mark Shapley of Keele University in England came up with a list of eight cancer "red flags."

It's possible to have one or more of these and not have cancer, but why take the chance? Dr. Shapley says doctors should follow up at once to pinpoint the cause.

Rectal Bleeding

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See blood in the bowl - or on your toilet paper? That could mean colon cancer, though the vast majority of people who "see blood" have hemorrhoids or another condition besides cancer.

"Piles (hemorrhoids) are very common, and for every 1,000 people at home with the symptoms of "rectal bleeding," less than one will have cancer," Dr. Mark Shapley of Keele University in England told CBS News in an email.

Iron-Deficiency Anemia

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Feeling tired, dizzy and have pale skin? Those can be signs of an iron deficiency and that can be a sign of something much worse.

Iron is needed to make hemoglobin, the protein that delivers oxygen to tissues throughout the body.

A deficiency can be caused by all sorts of conditions that aren't cancer, including heavy menstrual periods, ulcers, and a diet that is too low in iron. But since iron-deficiency anemia can also be evidence of colon cancer, it's essential that doctors take steps to find out the specific cause.

Breast Lump

Most breast lumps - perhaps as many as four out of five - are benign, according to the Mayo Clinic. But since lumps can be cancerous, your doctor should examine any lump just to make sure. Mammography and ultrasound tests can be helpful, as can a breast biopsy.

"Positive" Rectal Exam

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Doctors can check the prostate by sticking a gloved finger inside a man's rectum and checking the gland's size, shape, and hardness. If the prostate is enlarged, or if there is a lump, that could mean prostate cancer - although prostate abnormalities can also be evidence of a benign condition known as benign prostatic hyperplasia (prostate enlargement).

The good news is most men who go for additional testing do not have prostate cancer.

Blood in Urine

Most cases of blood in the urine have a benign cause. For example, exercise can cause the condition, which doctors call hematuria. But hematuria can also be evidence of urological cancer, so doctors should always follow up to pinpoint the cause.

Don't assume that just because urine isn't red it doesn't contain blood. In some cases, urine that appears normal contains red blood cells. Doctors can detect this "microscopic" hematuria via urinalysis.

Coughing Up Blood

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Coughing up blood can mean lung cancer, though the problem can have other causes ranging from violent coughing to a simple bloody nose.

The blood that comes up often appears bubbly because it is mixed with air and mucus. Doctors call the condition hemoptysis, and its cause should always be pinpointed.

Swallowing Difficulty

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Trouble swallowing, a.k.a. dysphagia, can be evidence of cancer of the head or neck or esophagus (throat).

Doctors should always follow up to find the root of the problem, which can also be caused by acid reflux (gastroesophageal reflux disease (GERD) - or simply a severe sore throat.

Post-Menopausal Bleeding

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Bleeding that occurs after menopause may be a sign of cancer, including that of the cervix, ovaries, uterus, or vagina. Doctors should pinpoint the problem via a variety of tests, including ultrasound and biopsy.