Home » Pet Health » Cancer 101 » Difference Between a Cancer Cell and a Normal Cell


Understanding the basics of cancer, like how cancer cells differ from normal cells, gives you the tools to comprehend and cope with your pet’s cancer diagnosis. As you might expect, normal cells and cancer cells are dissimilar in many ways. How they grow and function, are controlled, and affect other tissues, can all distinguish a normal cell from a cancer cell.


The process of cell division and cell death is highly regulated by a range of chemical and biological signals in a normal cell. The normal cell responds to the signals that enable their division or stop their division. Cancer cells, on the other hand, do not respond to these signals and grow or divide uncontrollably. Cancer cells can continue to grow, even if they are old or damaged. This results in the formation of an abnormal mass of cells referred to as a tumor.

A major reason for this difference in growth is that normal cells stop growing when enough cells are present around them to create contact with each other. This contact prevents normal cells from overgrowing and invading nearby tissues. In contrast, cancer cells continue to grow even if there are enough cells present around them to allow contact. As a result, the overgrowth of cancer cells can cause them to invade nearby tissues.


Another vital characteristic that distinguishes cancer cells from normal cells is their function. In normal cells, maturation allows the cells to become specialized and gain their designated functions. Cancer cells, on the other hand, divide so quickly that they don’t get a chance to mature properly, thus preventing them from becoming specialized with specific functions. For example, normal mature liver cells can perform metabolic functions, while cancerous liver cells fail to perform metabolic functions.


Under normal circumstances, when cells become damaged beyond repair, the immune system identifies them and has them removed. But cancer cells can trick the immune system and escape its effects, allowing continued cell growth, leading to tumor formation.

Effect on other tissues

While normal cells know their place in the body and stay where they belong, cancer cells can detach from their original location, migrate to other regions of the body, and continue their growth in that new location. This process is called metastasis. If you look at liver cancer as an example again, liver cancer cells may migrate from the liver into the lungs to create new growth there (known as metastatic liver cancer).

As you can see, cancer has mechanisms that can outsmart the typical processes used to control the body and maintain a healthy state. However, as a pet parent, you can help reduce your pet’s chance of developing cancer through a healthy diet and physical activity. If you suspect your furry friend may be at higher risk, monitor them regularly, especially as they age. Detecting cancer in its early stages can significantly improve cancer outcomes and give you many more happy years together.

The Pet Cancer Foundation’s Website Editorial team is comprised of veterinarians, veterinary oncologists, and veterinary technicians, as well as scientific writers and editors who have attained their PhD’s in the life sciences, along with general editors and research assistants. All content found in this section goes through an extensive process with multiple review stages, to ensure this extended resource provides pet families with the most up-to-date information publicly available.

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Keep Your Pets Healthy Editorial Team

Last Updated: October 13, 2022

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The following sources were referenced to write the content on this page: 

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Ribatti, D 2017, ‘A revisited concept: Contact inhibition of growth. From cell biology to malignancy’, Exp Cell Res., vol. 359, no. 1, pp. 17-19.

Sarkar, S, Horn, G, Moulton, K, Oza, A, Byler, S, Kokolus, S & Longacre, M 2013, ‘Cancer development, progression, and therapy: an epigenetic overview’, Int J Mol Sci., vol. 14, no. 10, pp. 21087-21113.

Vinay, DS, Ryan, EP, Pawelec, G, Talib, WH, Stagg, J, Elkord, E, Lichtor, T, Decker, WK, Whelan, RL, Kumara, H, Signori, E, Honoki, K, Georgakilas, AG, Amin, A, Helferich, WG, Boosani, CS, Guha, G, Ciriolo, MR, Chen, S, Mohammed, SI, Azmi, AS, Keith, WN, Bilsland, A, Bhakta, D, Halicka, D, Fujii, H, Aquilano, K, Ashraf, SS, Nowsheen, S, Yang, X, Choi, BK & Kwon, BS 2015, ‘Immune evasion in cancer: Mechanistic basis and therapeutic strategies’, Semin Cancer Biol, vol. 35 Suppl, pp. S185-s198.

Wu, JS, Jiang, J, Chen, BJ, Wang, K, Tang, YL & Liang, XH 2021, ‘Plasticity of cancer cell invasion: Patterns and mechanisms’, Transl Oncol, vol. 14, no. 1, p. 100899.

The Pet Cancer Foundation’s medical resource for pet owners is protected by copyright.

For reprint requests, please see our Content Usage Policy.