Difference Between Invasion and Metastasis

The key difference between invasion and metastasis is that invasion refers to the ability of cancer cells to direct extension and penetration into neighbouring tissues while metastasis refers to the ability of cancer cells to penetrate into lymphatic and blood vessels, circulate through the body, and invade normal tissues elsewhere in the body.

Cancer is an abnormal growth of cells. Naturally, a healthy cell has a mechanism to control its division. But during the development of cancer, cells undergo uncontrollable cell division. Hence, a mass of cells is produced as a result of it. Also, there are more than 100 identified cancers. Chemotherapy, radiation or surgery are the treatment procedures for cancer. However, in order to control cancer, it is necessary to prevent spreading of cancer into healthy tissues and cells. Generally, cancer cells are capable of spreading throughout the body rapidly. These cells use two mechanisms; namely, invasion and metastasis to spread in the body. By invasion, cancer cell penetrates into neighbouring cells and tissues. By metastasis, cancer cells move and spread into another location of the body. Invasion and metastasis are the key features of cancer cells that distinguish them from other normal cells.

CONTENTS

1. Overview and Key Difference
2. What is Invasion
3. What is Metastasis
4. Similarities Between Invasion and Metastasis
5. Side by Side Comparison – Invasion vs Metastasis in Tabular Form
6. Summary

What is Invasion?

Invasion is the mechanism by which cancer cells penetrate into surrounding or neighbouring tissues. Invasion signals the malignancy. When cancer cells grow, divide and expand rapidly by invading the surrounding tissues, adjacent tissues push away from their original locations. Benign tumours show invasion, but they do not show metastasis.

However, malignant tumours show metastasis. Furthermore, the local invasion is the initial step of developing secondary tumours and leading to metastasis. Unless cancer cells invade tissue and enter into blood vessels or lymph, it cannot show metastasis.

What is Metastasis?

Metastasis is a lethal process associated with cancers. It is the ability of cancer to move into a new location from the development site. In simple words, it is the capability of cancer cells to penetrate into blood vessels and lymphatic system and circulate throughout the body and invade a new tissue in order to grow and spread cancer. Once metastasis occurred, it is difficult to treat that cancer by removing the tumour from the original location. There is a chance of this particular cancer growing in new tissue. Therefore, these types of cancers are known as malignant cancers. Therefore, metastasis is the leading reason for the mortality of cancer patients as well as morbidity of cancers since it causes the development of a secondary tumour in new tissue.

Metastasis begins with invasion. Then these cells enter into the lymphatic system and vascular system by passing through the basement membranes and extracellular matrix. It is the process called intravasation. Once they penetrate into lymphatic and blood vessels, they circulate through the vascular system throughout the body (extravasation). At the end of the metastasis, these cells will attach at a new location and proliferate to produce a secondary tumour.

What are the Similarities Between Invasion and Metastasis?

• Invasion and Metastasis are key features of cancer cells.
• They are the mechanisms by cancer cells to spread cancer in tissues.
• In both mechanisms, cancer cells penetrate into new cells causing tumours.
• Also, tumour cell interaction with extracellular matrix components, epithelial-mesenchymal transition and angiogenesis are important factors in invasion and metastasis.

What is the Difference Between Invasion and Metastasis?

Invasion and metastasis are two mechanisms which facilitate the spreading of cancer cells into neighbouring tissues and distal organs respectively. Here, invasion refers to the ability of a tumour to expand into surrounding tissues while metastasis refers to the ability to penetrate into the vascular system and moving into a distal organ and growing newly. Hence, this is the key difference between invasion and metastasis. Also, in order to develop a secondary tumour, metastasis is a necessary factor while the invasion is the first step of metastasis. Therefore, this is also a difference between invasion and metastasis.

Furthermore, unlike invasion, metastasis is the most common reason for mortality and morbidity of cancer. The below infographic on difference between invasion and metastasis shows more differences between both.

Summary – Invasion vs Metastasis

Invasion and metastasis are two key features of cancer cells which allow to distinguish them from other cells. Invasion is the direct migration and penetration of cancer cells into neighbouring tissues. On the other hand, metastasis is the spreading of cancer cells into tissues and organs at a different location beyond the original place. Hence, this is the key difference between invasion and metastasis. However, both mechanisms facilitate the spreading of cancer cells into new tissues. But, unlike invasion, metastasis causes higher mortality in cancer patients since removing the tumour from one place will not be sufficient to cure the disease.  In metastasis, cancer cells circulate via the vascular system and establish in a new location causing a secondary tumour. Thus, metastasis is a serious condition than the invasion.

Reference:

1.Martin, Tracey A. “Cancer Invasion and Metastasis: Molecular and Cellular Perspective.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 1 Jan. 1970. Available here  

Image Courtesy:

1.”Tumor invasion into vein in a case of colorectal cancer, HE 1″By Patho – Own work, (CC BY-SA 3.0) via Commons Wikimedia 
2.”Metastasis illustration (1)”By National Cancer Institute (CC0) via Commons Wikimedia