In this Cancer Basics article, you’ll learn how to tell if you have cancer. Bedside Manners' mission is to empower cancer patients and survivors through medical enrichment. Enjoy!  Local Signs of Cancer How do you tell if you have cancer? The signs of cancer, which are visible to you as well as your healthcare provider, can vary. Remember in our article “What Causes Cancer” this disease is dangerous because it interferes with the normal functioning of our body’s organs and tissues. There are signs that can tell you there is something wrong with an internal organ (e.g. lung) as well as an external organ (e.g. skin). These signs may be seen locally, such as on the skin. Here are a few local signs of cancer: 1) Lumps or swellings that can be felt or seen under the skin 2) Blood in stool, urine, vagina