Certain cancer symptoms almost always prompt a visit to the doctor. A breast lump. A mole that changes in size, shape or color. Blood in the stool.

But there are other symptoms that most people ignore.

Startling new finding: In a study published in British Journal of General Practice, nearly half of people with a warning sign of cancer decided not to see a doctor about it, often because they thought the symptom was insignificant.

For the following symptoms, your first step is to visit your primary care physician who can perform the appropriate tests and/or refer you to a specialist.

Important: If you have any one of these symptoms in isolation, the likelihood of you having cancer is less than 1%. That doesn’t mean you should dismiss the symptom. But it does mean that you shouldn’t panic if it shows up.

HEARTBURN

Most likely cause: Gastroesophageal reflux disease (GERD).

But it could be a sign of: Esophagus or stomach cancer. Symptoms of heartburn can include burning pain or discomfort in the stomach, upper ­abdomen, chest and/or throat…and/or excessive burping, bloating or nausea after eating. If those symptoms are chronic, it’s time to see a doctor for a workup. You might have Barrett’s esophagus, a precancerous condition that is triggered by chronic inflammation and increases the risk for esophageal cancer. Or you might have H. pylori, a bacterial infection of the stomach that increases your risk for stomach cancer (and ulcers)—but is easily treatable with a two-week treatment that includes antibiotics and possibly a proton-pump inhibitor.

What to do: Ask your doctor if you need an esophagogastroduodenoscopy (EGD), in which an endoscope is used to explore your esophagus, stomach and duodenum (the first section of the small intestine). A biopsy can be taken during the procedure if there is suspicious-looking tissue.

ITCHING AFTER A HOT SHOWER

Most likely cause: Dry skin or a contact allergy to a cleansing product.

But it could be a sign of: Polycythemia vera, a common myeloproliferative disorder, a type of blood cancer. In the early stages of this cancer, histamine-containing mast cells (cells behind allergic reactions) become hypersensitive, causing the skin to react to hot water.

What to do: If you’re over age 40 (when this cancer most commonly occurs), ask your doctor for a complete blood count (CBC), which will detect an elevation of red blood cells, a feature of polycythemia vera.

EATING ICE

Likely cause: Iron deficiency.

But it could be a sign of: Gastrointestinal cancers, bladder cancer or any cancer that leads to blood loss. Called pica, this phenomenon—a compulsion to eat ice, sand, soil, clay, paper or chalk or to chew on something metallic—usually occurs during pregnancy and can be a sign of iron deficiency. But iron deficiency also can signal chronic internal blood loss, sometimes from cancer.

What to do: Ask your doctor about a blood test for iron deficiency. If you have an iron deficiency, work with your doctor to determine the cause.

UNBEARABLE PAIN IN A BONE WHEN TOUCHED

Most likely causes: Trauma, rheumatological disease or infection.

But it could be a sign of: Bone metastases (the spread of an original, primary tumor into the bone). This symptom is a hallmark of bone cancer.

What to do: If you have unexplained pain that tends to increase over a month—particularly if it’s sensitive to the touch—talk to your doctor about ­imaging studies, such as a CT scan, a bone scan, an X-ray or an MRI.

DIARRHEA PLUS FACIAL FLUSHING

Likely cause: Irritable bowel syndrome (IBS).

But it could be a sign of: Neuroendocrine tumor, metastasized to the liver. Diarrhea alone rarely leads to a diagnosis of cancer, but diarrhea and flushing of the face are a unique pair of symptoms that could indicate a neuroendocrine tumor—a type of cancer arising from the hormone-­producing cells in the body.

What to do: Talk to your doctor about possible imaging (CT, PET or MRI) to potentially detect liver metastases and primary tumor.

REDDENED SKIN ON THE BREAST

Likely cause: Skin infection.

But it could be a sign of: Breast cancer. A lump is not the only warning sign of breast cancer. Redness of the breast—particularly if the skin also is thickened, with the texture of an orange peel—is a sign of inflammatory breast cancer, a rare and aggressive form of the disease that can be missed by a mammogram, an ultrasound or an MRI.

What to do: Ask your doctor about a breast biopsy, the best way to detect this type of cancer. Important: If the doctor diagnoses the redness as an infection and treats it with antibiotics, and the redness doesn’t resolve or worsens, return quickly for a follow-up examination.

BLOOD CLOT

Likely causes: Leg or arm injury, such as a sprained ankle…recent hospitalization or surgery…a long period of inactivity, such as a plane ride.

But it could be a sign of: Breast, pancreatic, ovarian and many other cancers. A blood clot (a symptom of deep vein thrombosis, or DVT) is a common ­problem, affecting 900,000 Americans yearly. But DVT is not commonly understood as a potential early warning sign of cancer and so is often overlooked as a cancer symptom, even though as many as one in 10 patients with an unexplained blood clot may have some type of cancer.

What to do: If you have a blood clot (typically signaled by a sudden, painful swelling of an arm or a leg) without any of the common triggers (see common causes above), talk to your doctor about a workup for cancer. This is an early warning sign that often is missed.

BLOATING

Likely cause: Eating too much or too fast.

But it could be a sign of: Ovarian cancer. Bloating is a common symptom that is rarely a sign of cancer. But persistent bloating can be a sign of cancer in the peritoneal cavity, a common feature of advanced ovarian cancer, particularly if accompanied by a persistent, dull ache in the abdomen and unexplained weight loss (a symptom of advanced cancer).

What to do: Your doctor may recommend a CT scan or a transvaginal ultra­sound. If the results are negative, ask about getting a laparoscopy, in which a thin, lighted tube is put through an incision in the belly to look at the abdominal and reproductive organs. A CT scan or a transvaginal ultrasound can easily miss ovarian cancer.

QUITTING SMOKING EASILY

Likely cause: You decided to quit, and you succeeded.

But it could be a sign of: Lung cancer. A chronic smoker who suddenly finds it unusually easy to quit may be experiencing a strange physiological symptom of lung cancer—­inexplicably losing the desire to smoke. Usually, non-small-cell lung cancer is diagnosed three to four years after a chronic smoker easily quits, and small-cell lung cancer (a more aggressive type) is diagnosed about six months after quitting.

What to do: If you have been a lifelong smoker who suddenly finds it easy to quit, talk to your doctor about having a chest CT scan for lung cancer. You also would benefit from routine annual surveillance even if the scan is negative.