Benign and Malignant Tumors

Tumours are groups of abnormal cells that form lumps or growths. Different types of tumours grow and behave differently, depending on whether they are non-cancerous (benign) or cancerous (malignant). Precancerous conditions have the potential to develop into cancer.

Benign tumours

Benign tumours are non-cancerous. They rarely cause serious problems or threaten life unless they occur in a vital organ or grow very large and press on nearby tissues. Benign tumours tend to grow slowly and stay in one place, not spreading into other parts of the body.

Once removed by surgery, benign tumours dont usually come back (recur). Benign tumours usually stay non-cancerous, except in very rare cases.

Precancerous conditions

Precancerous (premalignant) cells are abnormal cells that may develop into cancer if they arent treated. Some cells develop mild changes that may disappear without any treatment. Other cells pass on genetic changes and new cells gradually become more and more abnormal until they turn into cancer. It can take a long time for this to happen.

  • Precancerous (or premalignant) changes can vary in their degree of abnormality.
  • Hyperplasia an abnormal increase in the number of cells
  • Some hyperplasias are precancerous, but most are not.
  • Atypia (atypical) cells look slightly abnormal under a microscope
  • Sometimes atypia refers to changes caused by healing and inflammation, rather than a precancerous change, and the cells go back to normal once inflammation goes away or the body heals.
  • Metaplasia cells look normal under a microscope, but are not the type normally found in the that tissue or area
  • Metaplasias are usually not precancerous.
  • Dysplasia cells develop abnormally, have an abnormal appearance and are not organized like normal cells

Dysplasia almost always refers to a precancerous condition.

People with precancerous conditions are usually checked regularly, so they can be treated quickly if cell changes become more severe.

Malignant tumours

Malignant tumours are cancerous. Cancer can start in any one of the millions of cells in our bodies. Cancer cells have a larger nucleus


The part of the cell that holds the chromosomes, which contain DNA (genetic information). That looks different from a normal cells nucleus, and cancer cells behave, grow and function quite differently from normal cells.

Malignant tumours vary in size and shape. They grow in an uncontrolled, abnormal way and can grow into (invade) nearby tissues, blood vessels or lymphatic vessels. They can interfere with body functions and become life-threatening.

Cancer cells can break off and spread to distant locations in the body (metastasize). Cancer that spreads from its original location (the primary tumour) to a new part of the body is called metastatic cancer. Malignant tumours can also come back (recur) after they are removed.

How cancer spreads

Cancer cells can spread from where they started to other parts of the body, where they can grow into new tumours. This process is called metastasis.

Cancer can spread in 3 ways:

  • Invasion (direct extension) The tumour grows into surrounding tissues or structures.
  • Through the bloodstream (hematogenous spread) Cancer cells break away from the tumour, enter the bloodstream and travel to a new location in the body.
  • Through the lymphatic system Cancer cells break away from the tumour and travel through the lymph vessels and lymph nodes to other parts of the body.

The type of cancer and where it starts often influences if and where it will spread. The extent that cancer has spread when a person is diagnosed is called the stage. Many cancers follow a staging system from 0 to 4. Knowing how and where a cancer may spread helps doctors predict its possible course, plan treatment and further care.

These terms are also used to describe whether and how far cancer has spread:

  • Localized The cancer is confined to the original site.
  • Regional spread The cancer has grown into surrounding tissues or nearby lymph nodes.
  • Metastasis The cancer has spread to a distant organ of the body or lymph nodes far from the original (primary) tumour.

Its possible for cancer to spread anywhere in the body, but its most likely to go from its original site to other places in the body such as the bones, brain, liver or lungs.