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Causes & Symptoms

What causes cancer?

Not all causes of cancer are fully understood and many types of cancer have causes that are unknown. It is unclear why one person gets cancer while another doesn't, even when the same risk factors are shared.

Doctors and scientists do understand some common causes of cancer. For example, smoking is the major cause of lung cancer, and sunlight is the major cause of skin cancer.

Despite the unclear causes of many types of cancer, there are still many risk factors related to cancer.  A risk factor is something closely connected to cancer that increases the likelihood of developing cancer.

What are the symptoms of cancer?

There are many different symptoms of cancer. Some cancers don't have symptoms, while others have symptoms that don't appear till long after the cancer has started and has become serious. Symptoms of cancer can show up in various ways throughout the body:
Changes to general well-being:

  • Fevers, chills, and night sweats

  • Sudden, unintended weight changes

  • Chronic pain

  • A general feeling of sickness or a persistent sense of not feeling well

  • Muscle or joint pain that won't go away

Changes related to energy levels:

  • Constant tiredness and fatigue

  • Difficulty sleeping

Changes to skin:

  • Lumps under the skin

  • Other changes to skin like changes in color, sores, and changes in moles

  • Bleeding or bruising

Changes related to eating, breathing, and digestion:

  • Loss of appetite

  • Changes in bowel or bladder habits

  • Persistent cough or trouble breathing

  • Difficulty swallowing

  • Hoarseness

  • Persistent indigestion or discomfort after eating

  • Persistent diarrhea, constipation, or bloody stools

If you have any of these symptoms or any other symptoms that concern you, make an appointment with your doctor.