Tumour cells may either remain in their original location (benign) or spread and invade neighbouring tissue (malignant)

• Benign tumours do not cause cancer as they grow slowly and have distinct borders (do not encroach on surrounding tissues)

Metastasis is the spread of cancer from one location (primary tumour) to another, forming a secondary tumour

• Secondary tumours are made up of the same type of cell as the primary tumour – this affects the type of treatment required
  

  • E.g. If breast cancer spreads to the liver, the patient has secondary breast cancer of the liver (treated with breast cancer drugs)

Cancer diagnoses can be made be determining the mitotic index of a particular tissue

• The mitotic index represents the number of cells in mitosis (dividing) as a percentage of the total number of cells

• If the mitotic index is higher than standard, this would suggest that a tissue is cancerous