Routine tests and checkups, like pap smears and colonoscopies, are important -- but don't rely on tests alone to protect you from cancer. It's just as important to listen to your body and notice anything that's different, odd, or unexplainable. Although many of these symptoms could be caused by less serious conditions, they're worth getting checked out if they persist. You don't want to join the ranks of cancer patients who realize too late that symptoms they'd noticed for a long time could have sounded the alarm earlier, when cancer was easier to cure.

A red, sore, or swollen breast
Everyone knows to check for lumps in the breasts, but too often symptoms closer to the surface – which can indicate inflammatory breast cancer -- are overlooked. Some women describe noticing cellulite-like dimpled skin on an area of the breast. Others noticed that a breast felt swollen, hot, or irritated. Red or purplish discoloration is also cause for concern. Call your doctor about any unexplained changes in your breasts.

Nipple changes
One of the most common changes women remember noticing before being diagnosed with breast cancer is a nipple that began to appear flattened, inverted, or turned sideways. "My nipple started looking like it was turned inside out," said one woman. In addition, inflammatory breast cancer also causes nipple problems, such as itchy, scaly, or crusty skin on the nipple -- so take any nipple changes seriously.

Bloating or abdominal weight gain -- the "my jeans don't fit" syndrome
While this might sound too common a phenomenon to be considered a cancer symptom, consider this: Women diagnosed with ovarian cancer overwhelmingly report that unexplained abdominal bloating that came on fairly suddenly and continued on and off over a long period of time (as opposed to occurring a few days each month with PMS) was one of the main ways they knew something was wrong.

Feeling full and unable to eat
This is another tip-off to ovarian cancer; survivors say they had no appetite and couldn't eat, even when they hadn't eaten for some time. Any woman who experiences noticeable bloating or weight gain numerous times (the diagnostic criteria is more than 13 times over the period of a month) -- especially if it's accompanied by pelvic pain or feeling overly full -- should call her doctor and ask for a pelvic ultrasound.

Unusually heavy or painful periods or bleeding between periods
Many women reported this as the tip-off to endometrial or uterine cancer. Unfortunately, many women also said their doctors weren't responsive, overlooking or misdiagnosing their complaints as normal perimenopause. Ask for a transvaginal ultrasound if you strongly suspect something more than routine heavy periods.

Erection problems
As prostate cancer progresses, a common sign is difficulty getting or sustaining an erection. This can be a difficult subject to talk about, but it's important to bring it to your doctor's attention. It could be a sign of sexual dysfunction with another cause, of course, but it's a reason to have an exam and possibly a PSA test.

Pain, aches, or heaviness in the groin, hips, thighs, or abdomen
One sign of prostate cancer is frequent pain in the hips, upper thighs, or the lowest part of the back. Men with testicular cancer report noticing a heavy, aching feeling low in the belly or abdomen, or in the scrotum or testicles themselves. They sometimes describe it as a feeling of downward pulling or as a generalized ache throughout the groin area. Prostate cancer that has spread to the lymph nodes often makes itself known as discomfort in the pelvis or swelling in the legs.

Testicular swelling or lump
The lumps that indicate testicular cancer are nearly always painless. It's also common for a testicle to be enlarged or swollen but lacking any specific lump that you can see or feel. Some men report feeling discomfort from the enlargement but not an outright pain.

Scaly or painful nipple or chest, nipple discharge
Men do get breast cancer; they also get a condition called gynecomastia, which is a benign lump in the breast area. Breast cancer is usually detected as a lump, but if it's spreading inward it can also cause chest pain. Other signs of breast cancer include patches of red, scaly, or dimpled skin or changes to the nipple such as turning inward or leaking fluid. Bring any lump, swelling, or skin or nipple problem, or any chest pain, to your doctor's attention.

Difficulty urinating or changes in flow
Hands-down, the most common early sign of prostate cancer is a feeling of not being able to start peeing once you're set to go. Many men also report having a hard time stopping the flow of urine, a flow that starts and stops, or a stream that's weaker than normal. Any of these symptoms can have less serious causes, but it’s still reason to see your doctor for an exam and a possible screening test for prostate-specific antigen (PSA).

Pain or burning during urination
This symptom can also indicate a urinary tract infection or sexually transmitted disease, of course, but in any case it warrants an immediate trip to the doctor. It's often combined with the feeling that you need to go more often, particularly at night. This same symptom can also indicate inflammation or infection in the prostate or benign prostatic hyperplasia, the name for what happens when the prostate grows bigger and blocks the flow of urine. However, you need to get checked out to tell the difference.

Wheezing or shortness of breath
One of the first signs lung cancer patients remember noticing when they look back is the inability to catch their breath. "I couldn't even walk across the yard without wheezing. I thought I had asthma, but how come I didn't have it before?" is how one woman described it. Thyroid cancer can also cause breathing problems if a nodule or tumor begins to press on the trachea, or windpipe. Any breathing difficulties that persist are reason to visit the doctor.

Swallowing problems or hoarseness
Most commonly associated with esophageal or throat cancer, difficulty swallowing is sometimes one of the first signs of lung cancer, too. A hoarse or low, husky voice or the feeling of something pressing on the throat can be an early indicator of thyroid cancer or a precancerous thyroid nodule, as can the feeling of having something stuck in your windpipe.

Frequent fevers or infections
These can be signs of leukemia, a cancer of the blood cells that starts in the bone marrow. Leukemia causes the marrow to produce abnormal white blood cells, which crowd out healthy white cells, sapping the body's infection-fighting capabilities. Often, doctors diagnose leukemia only after the patient has been in a number of times complaining of fever, achiness, and flu-like symptoms over an extended period of time.

Upset stomach or stomachache
As simple as it sounds, a good old-fashioned bellyache is what tipped off a number of lucky folks, whose doctors ordered ultrasounds and discovered early that they had tumors on their livers. Stomach cramps or frequent upset stomachs may indicate colorectal cancer; many cancer patients say their doctors thought they had ulcers.

Weakness and fatigue
"I kept having to sit down at work, and one night I was too tired to drive home," said one woman in describing the fatigue that led her to discover she had leukemia. Generalized fatigue and weakness is a symptom of so many different kinds of cancer that you'll need to look at it in combination with other symptoms. But any time you feel exhausted without explanation and it doesn't respond to getting more sleep, talk to your doctor.

Unexplained weight loss
If you notice the pounds coming off and you haven't made changes to your diet or exercise regime, you need to ask why. Weight loss is an early sign of colon and other digestive cancers; it's also a sign of cancer that's spread to the liver, affecting your appetite and the ability of your body to rid itself of wastes.

Changes in nails
Unexplained changes to the fingernails can be a sign of several types of cancer. A brown or black streak or dot under the nail can indicate skin cancer, while newly discovered "clubbing" -- enlargement of the ends of the fingers, with nails that curve down over the tips -- can be a sign of lung cancer. Pale or white nails can be an indication that your liver is not functioning properly, sometimes a sign of liver cancer.

Chronic "acid stomach" or feeling full after a small meal
The most common early sign of stomach cancer is pain in the upper or middle abdomen that feels like gas or heartburn. It may be aggravated by eating, so that you feel full when you haven't actually eaten much. What's particularly confusing is that the pain can be relieved by antacids, falsely confirming your conclusion that it was caused by acid in the stomach, when it's more than that. If you have frequent bouts of acid stomach, an unexplained abdominal ache, or a full feeling after meals even when you're eating less than normal, call your doctor.

Chronic heartburn
If you just ate half a pizza, heartburn is expected. But if you have frequent episodes of heartburn or a constant low-level feeling of pain in the chest after eating, call your doctor and ask about screening for esophageal cancer. Gastroesophageal reflux disease (GERD) -- a condition in which stomach acid rises into the esophagus, causing heartburn and an acidic taste in the throat -- can trigger a condition called Barrett's esophagus, which can be a precursor of esophageal cancer.

Bowel problems
Constipation, diarrhea, and changes in stools can all be signs of cancer. As with many othercancer symptoms, the way to tell if this is cause for concern is if it goes on for more than a few days without a clear cause, such as flu or food poisoning. People diagnosed with colon cancer say they noticed more frequent stools, as well as a feeling that their bowels weren't emptying completely. One of the early signs of pancreatic cancer is fatty stools, which can be recognized as frequent, large stools that are paler than normal and smelly. This is a sign that your body's not absorbing your food normally, and it should be brought to your doctor's attention.