How Does Metastasis Occur?

July, 2022 - Last update: January, 2024

The Basics:

A tumour occurs when cells grow uncontrollably or do not die when signaled to. This creates an abnormal mass in the body. There are two types of tumours: benign and malignant. A benign tumour does not have the possibility to metastasize, whereas a malignant tumour has the likelihood of metastasizing. 

What does Metastasis mean?

Metastasis is the spreading of a malignant tumour into other parts of the body, beyond the point of origin. The metastatic cells can travel through your bloodstream or lymphatic system to distant parts of the body away from where the tumour originated. 

How does this happen?

There are a few steps that occur when cancer spreads in the body:

  • Metastasis starts with the invasion of tumour cells into the neighbouring tissue.
  • The cancerous cells break off and migrate into either blood vessels or lymph vessels.
  • The cells must be able to move through the body’s circulatory system and/or lymphatic system without being killed by our body’s defenses.
  • The cells then exit the vessels of the circulatory system/ lymphatic system into a new organ.
  • Lastly, proliferation (rapid production) of the cancerous cells occurs in the new organ(s). 

This process is considered to be inefficient because most of the time, the spreading cells die before reaching the target organ and proliferating. These coordinated steps must occur favourably for the cells in order for a new tumour to be generated in another part of the body. 

What types of cancers are more likely to metastasize?

All cancer types have the potential to be metastatic. The more common cancer types include: 

  • Breast cancer
  • Prostate cancer
  • Lung cancer
  • Kidney cancer
  • Thyroid cancer
  • Colon cancer
  • Pancreatic cancer
  • Bone cancer 
  • Liver cancer  
  • Ovarian cancer
  • Stomach cancer 


The main goal of treatment for metastatic cancers is to slow or stop the growth of the cancer. This can be done through chemotherapy, immunotherapy and radiation therapy to name a few. Another way to treat metastatic 

cancer is by treating the symptoms, also known as palliative care. If the cancer is controlled, the patient can live for several years and through palliative care, the quality of life is improved. 

Diagnosis and Prevention:

In order to determine if a tumour has metastasized, imaging is done to see inside the body. This can be done through an ultrasound, X-ray, CT scan, bone scan, MRI scan, or PET scan. Metastasis cannot necessarily be prevented, but if caught at an early stage, early treatments can be done to control the spread. Whole Body MRI scans can help detect cancer early by imaging the full body from head to just below the knees in one scan. 

Bottom Line:

Early detection of cancer is paramount. This allows for early treatment planning and a better prognosis. Metastasis occur most often with untreated cancers. 

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