When doctors think someone might have cancer, there are several important signs and symptoms to look out for. Here are some of the key ones:

1. Unexplained Weight Loss:

   • Losing a lot of weight, like more than 10% of your total body weight in 6 to 12 months, can be a warning sign. About 40% of people with cancer notice they have lost weight for no reason.

2. Persistent Pain:

   • If you have pain that gets worse over time or doesn’t get better with regular treatments, it might be a sign of something serious. For example, back pain could be linked to tumors in the spine.

3. Changes in Bowel or Bladder Function:

   • If you notice ongoing changes like diarrhea or constipation, or see blood in your urine or stool, you should see a doctor. About 20% of people with colorectal cancer notice changes in their bowel habits.

4. Skin Changes:

   • Keep an eye out for new or changing moles, or skin sores that don’t seem to heal. These can be signs of skin cancer. Malignant melanoma is a type of skin cancer that makes up 5-7% of all skin cancers but causes many skin cancer deaths.

5. Unusual Bleeding or Discharge:

   • If you're bleeding for no clear reason, like in the case of uterine cancer, or if you have unusual discharge, this can be an important sign. About 25% of people with uterine cancer experience symptoms like these.

6. Lumps or Masses:

   • Bumps or masses you can feel can indicate something more serious. Around 60% of people with breast cancer report feeling a lump.

Doctors need to think about these symptoms along with a person’s medical history and use imaging tests to make a proper diagnosis.