13 Unusual Cancer Symptoms You Shouldn’t Overlook

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On September 17, 2025

We’ve all experienced common issues like headaches, vision changes, nausea, stomach pain, and mouth sores. These don’t tend to cause us much worry because they’re usually symptoms of benign issues such as the common cold, stomach bug, or just needing a new glasses prescription. But if a new symptom stays persistent and is unexplained, it’s worth investigating.

“Those are things that really should catch someone’s attention,” says Joshua Cohen, MD, medical director of the Gynecologic Cancer Program at City of Hope Orange County in Irvine, California. “Call your healthcare provider and say, ‘Can I come in or talk with you or someone from the office to review how I’m feeling?’”

Here are 13 weird symptoms that are worth discussing with a doctor, as they could sometimes be warning signs of cancer.

1. Unexplained Weight Loss

You expect to lose weight when you cut calories or exercise more than usual. But a rapid, significant drop in weight — especially a loss of 10 pounds or more — without an obvious cause can signal a problem.

Weight loss is often one of the first warning signs of cancer, especially cancers of the lungs, stomach, pancreas, and esophagus. One reason is that cancer cells burn more calories than healthy cells. Also, as the immune system fights cancer, it releases inflammatory chemicals that disrupt normal metabolism and appetite.

2. Persistent Headache

Millions of Americans regularly get migraines and headaches.

While a severe headache might feel scary, it rarely suggests something serious, unless it comes with symptoms like seizures, nausea and vomiting, weakness, or numbness — or it happens frequently and doesn’t go away.

How long the headache lasts is also an important factor. “A day or two is fine, but a week, two weeks, three weeks of persistent headaches — that’s not normal,” says Dr. Cohen.

3. Vision Changes

Blurriness, double vision, or vision loss usually stem from a problem with the eye. It may be that your glasses prescription has changed or you’ve developed a condition like cataracts. Rarely, tumors can develop in or around the eye and affect vision. Although much less common, a brain tumor can affect vision when it puts pressure on the optic nerve or other areas of the brain that process sight.

See an ophthalmologist if you have symptoms like blurred or double vision, floaters, flashes, distorted vision, abnormal eye movements, sensitivity to light, or vision loss. If you also have severe headaches, seizures, or weakness, seek medical attention urgently, as these symptoms can occur with a brain tumor.

4. Frequent Belching

Heartburn and belching after a meal probably means that you’ve eaten too many spicy or fatty foods. Sometimes, though, heartburn and frequent burping can be warning signs of cancer — particularly esophageal or stomach cancer.

People who’ve lived with untreated gastroesophageal reflux disease (GERD) for a long time are at higher risk for esophageal cancer.

Experts recommend that anyone who’s had GERD for more than five years, has reflux symptoms weekly or more, and has at least two risk factors (such as being male, age over 50, obesity, or history of smoking) get an endoscopy to screen for esophageal cancer.

Burping can be a symptom of stomach cancer at any stage, and it’s caused by a tumor in the stomach blocking the passage of air. If you’re belching frequently and have other symptoms like stomach pain that doesn’t go away, nausea, feeling full after eating only a small amount of food, bloating, and heartburn, tell your doctor. They may want to do some testing, including endoscopy, to find the cause.

5. Mouth Sores

Oral cancer sometimes appears as sores on the lip or inside the mouth. The difference between a sore that happens from an injury (like biting your lip) and a cancer sore is that a cancer sore won’t heal within a couple of weeks.

Oral cancer is very rare, affecting only 11 out of 100,000 people during their lifetime. Even so, a nonhealing sore or rough spot in your mouth that doesn’t go away is worth seeing your dentist or primary care doctor about.

6. Hoarseness

It’s normal to have a hoarse or raspy voice when you’ve been talking or singing too much, or if you have laryngitis. Hoarseness that doesn’t improve after a couple of weeks, or that is accompanied by a lump in your throat or painful swallowing can be a symptom of laryngeal cancer. The odds of developing this cancer are higher in people with human papillomavirus (HPV) and in frequent tobacco and alcohol users.

7. Night Sweats

If you’re waking up at night drenched in sweat, any one of several conditions affecting your body’s thermostat could be to blame. An overactive thyroid gland, obstructive sleep apnea, an autoimmune disease, and menopausal hormone changes all cause night sweats. A cancer like leukemia or lymphoma is another possible cause of this symptom, but usually the sweating comes with other symptoms, such as unexplained weight loss or a fever.

8. Unusual Spotting or Bleeding Between Periods

Everyone’s menstrual cycle is different, but some types of bleeding are more concerning than others. “If someone’s bleeding between periods or bleeding with sexual activity, those are not normal,” Cohen says. “Talk to your ob-gyn or primary care doctor about it.”

Bleeding between periods could be from stress, hormone changes, or weight changes. Yet it’s also a sign of cervical, ovarian, and uterine cancer.

9. Clubbed Fingers

Nail clubbing makes the ends of the fingers widen and look like spoons. Toes can get that clubbed appearance, as well. Although clubbing itself isn’t harmful, in rare cases it’s a warning sign of lung cancer. One theory is that low oxygen levels from the cancer trigger the release of vascular endothelial growth factor (VEGF), a protein that increases blood vessel formation and permeability of vessel walls, leading to fluid build up under the nails.

10. Changes in Peeing or Pooping

Constipation, pencil-thin poops, and an urgent need to pee are sometimes symptoms of gynecologic and colon cancers.

Because these are also symptoms of many other, noncancerous conditions, they can be hard to pinpoint.

“For pelvic cancers, a lot of the symptoms are nondescript, unfortunately, and that’s why it’s really important to be vigilant,” Cohen says. Any changes to your bowel and bladder habits that don’t improve or don’t have an obvious cause should prompt a doctor visit.

11. Breast Changes

A lump might be the most obvious breast cancer symptom, but it isn’t the only one. Any breast changes could be warning signs, including redness or flaking of the skin, an inverted (turned in) nipple, an orange peel–like texture to the skin, or one breast that’s grown larger than the other.

“These are all things that you should talk to your healthcare provider about,” says Cohen.

12. Dark Line Under a Fingernail

A thin dark line that runs from top to bottom across the nail is a symptom of subungual melanoma. This rare skin cancer grows in skin pigment cells called melanocytes under the nail. It most often affects the thumb, index finger, or big toe. The line starts out thin but gradually gets thicker. Because subungual melanoma is a very aggressive form of melanoma, it’s important to see a dermatologist or other healthcare provider right away for a diagnosis.

13. Pain After Drinking Alcohol

Swollen lymph nodes often occur when you have an infection, but a lump that feels painful after you drink alcohol is a possible sign of Hodgkin lymphoma. Fever, night sweats, and weight loss are other common symptoms of this blood cancer that affects the lymphatic system.

Hodgkin lymphoma is very curable when it’s caught and treated early.

When to See a Doctor

New symptoms like these shouldn’t necessarily cause you to panic. Most of the time, the cause isn’t cancer. Still, it’s important to know what’s normal for you, and to talk to a doctor if something feels unusual — especially if the symptom doesn’t improve after a couple of weeks or it gets worse. “If you have concerns and you’re worried, it’s never wrong to reach out,” says Cohen.

The Takeaway

Symptoms like belching, changes in bladder or bowel habits, and a hoarse voice usually don’t signal a serious health condition, but rarely, they can be signs of cancer if they persist with no obvious cause.
Knowing your body and what’s normal for you can help you spot a problem early.
Report any symptoms that persist for more than a couple of weeks or get worse to a doctor.