What are the warning signs of cancer?

Common symptoms: Specific symptoms such as a changing mole (melanoma), difficulty swallowing (esophageal cancer), enlarging lymph glands (lymphoma), bloody stools (colon & rectal cancer), blood sputum (lung cancer). Also general things such as unexplained weight loss, low blood levels, persistent fevers, severe fatigue, progressive shortness of breath, etc.

Depends: Some cancers can have signs and symptoms while others don't until advanced stages. Development of any symptoms that are especially persistent and worsening and a general change in health for the worse including a general sense of non well being, yo should be evaluated by a doctor for a thorough workup.