October 18, 2023


A tumour is a mass or group of abnormal cells that form in the body. Although there are many different types of tumours they are typically divided into two categories: benign which means non-cancerous and malignant which means cancerous. Malignant tumours are further divided into carcinoma, sarcoma, lymphoma, and melanoma. Some tumours may also be precancerous, which means they have the potential to become cancerous if not treated.

What is the difference between a benign tumour and a malignant tumour?

Malignant (cancerous) tumours can grow and spread into nearby tissues and other parts of the body. They can also come back after treatment. Benign (non-cancerous) tumours do not spread and are rarely life-threatening. However, some benign tumours may need treatment if they cause problems such as pain, pressure or bleeding. Precancerous tumours are usually treated to prevent them from turning into cancer.

How do pathologists decide if a tumour is benign or malignant?

One of the most important roles that a pathologist plays in your medical care is determining whether a tumour is benign or malignant. By examining tissue from the tumour under the microscope, pathologists can reliably tell the difference between benign and malignant in most circumstances.

Features typically seen in malignant (cancerous) tumours:

  • Invasion – Invasion is a word pathologists use to describe the spread of tumour cells into the surrounding normal tissue.
  • Perineural invasion – Perineural invasion means that tumour cells have become attached to a nerve inside or near the tumour.
  • Lymphovascular invasion – Lymphovascular invasion is the spread of tumour cells into blood vessels or lymphatics. Once tumour cells enter a blood vessel or lymphatic space they can metastasize (spread) to other parts of the body.
  • Metastatic disease – A metastasis is a group of tumour cells that have travelled to another part of the body. Common locations for metastasis include lymph nodes, the liver, the lungs, and bones.
  • Necrosis – Necrosis is a type of cell death commonly seen in malignant tumours.
  • Mitotic activity – Cells in the human body divide by a process called mitosis and pathologists use the term mitotic activity to describe the number of dividing cells in a tissue. Because malignant tumours tend to grow faster than benign tumours, it is common for malignant tumours to show greater mitotic activity or to have more mitoses.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have a question about this article or your pathology report.

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Other helpful resources

Atlas of Pathology
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