How can you tell the difference between a healthy body and somebody with a disease e.g. Cancer?

Question: How can you tell the difference between a healthy body and somebody with a disease e.g. Cancer?
- Keywords:
  body,
  cancer,
  disease,
  healthy
Asked by 889dagg46 to Vaanu on 8 Nov 2016.
- Vaanathi Sundaresan answered on 8 Nov 2016:
  
  There are so many ways of doing this:
  1. Early stage: there would not be much symptoms. SO only a routine health checkup can reveal this. There are so many types of imaging techniques such as PET (positron emission tomography), CT etc for determine the stage and development of tumour.
  2. developing stage: Some symptoms. This is the final reversible stage where the person should not ignore/overlook the symptoms and have to undergo screening promptly. The tumours are detected by various imaging techniques. 3. Acute stage: The patient suffers from heavy pain and other symptoms – treatment to lengthen the lifetime a narrow margin is possible but not cure.
  
  Now, on the acquired images, cancers or tumours occurs like cyst like manifestation, or swelling, degenerated areas, blood leakage, discoloured areas depending on the type of tumours. Basically we look out for any anomalies (structures different from normal tissue appearance) and try to categorise the signs with the help of clinicians.

Question: How can you tell the difference between a healthy body and somebody with a disease e.g. Cancer?