Pathology dictionary

What does malignant mean?

In medicine, the word malignant is used to describe a cancerous growth of cells. A group of cells are considered malignant when they have developed the ability to:

  • Grow uncontrollably.
  • Damage surrounding normal tissue.
  • Spread to other parts of the body.

Malignant tumours can start anywhere in the body and the behavior of the tumour depends on many factors such as:

  • The type of tumour.
  • The size of the tumour.
  • The tumour grade.
  • The amount of tumour invasion into the surrounding normal tissue.

All of these factors are examined by your pathologist and documented in the pathology report.

Importantly, not all malignant tumours behave the same. For example, some tumours, despite being malignant, are slow growing and frequently cured while other malignant tumours are almost always fatal. The pathology report provides critical information which will allow your doctor to predict the behavior of the tumour and select the most appropriate treatment (prediction of behavior is referred to as prognosis).

Some malignant tumours that have not yet spread into the surrounding tissue are called carcinoma in situ. These tumours are also called non-invasive and they are considered a precursor disease because they can turn into an invasive tumour over time.

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