Heart diseases and cancer are certainly the most common diseases of our era. However, these major types of diseases never combine. It seems like the heart benefits from some sort of immunity against cancer, but how?

We know that there are several forms of cancer affecting different organs such as prostate, liver, breast, pancreas, skin etc. However, there is no heart cancer, well almost...

[Image credits: Wikimedia.org]

Like any other organ, the heart can be touched by cancer when it's generalized ( metastasized) ,for example a cancer of the lungs has high chances of reaching the pericardium. As Mayo Clinic points out, the heart can also be affected when someone is suffering from a certain condition called rhabdomyosarcoma, which is not a cancer of the heart itself, but a soft tissue cancer.Luckily this condition is very rare.

The answer lies in cardiac myocytes (or cardiomyocytes), the most abundant cells that make up the heart muscle. The heart is differentiated from other organs, it's just like a "big pile of muscles". These cells have the main characteristic of being in their terminal phase of differentiation, meaning they stop their cell cycle quite early in life.You are probably wondering '' but the heart grows with age! '' well, that's right but only through an expansion of the size of the cells.

Cardiomyocytes are therefore different from the epithelial cells that make up most other organs which have never given up cell division, respond to external and internal stimulus and they are able to increase in number if needed.

Cancer is by definition an uncontrolled cell proliferation.In fact, genetic mutations accumulate in cells over time, leading to unregulated cell division, thus a new type of cells appear in the concerned organ.The result is the formation of a tumor that eventually becomes malignant can become metastatic and spreads attacking other organs and tissues.

There are several possible ways to develop cancer but the two main prototypes are either an activation of an oncogene or an inactivation of a tumor suppressor gene.Oncogenes are genes found in normal cells and they are responsible for cell division, usually, their activity is inhibited by tumor suppressor genes which are genes that control any abnormal division.

[Image credits: Wikimedia.org]

The heart is almost never touched by this scenario because on one hand primary tumors are very rare and on the other because the process of heart growth no longer integrates cell division very early in life. The heart is therefore much more likely to be affected by generalized cancers.

Unfortunately, the body is much more complex than that, and primary heart tumors do exist but they are extremely rare.According to surgery and autopsy reports, their incidence rate is about 0.3% to 0.7% of all cardiac tumors and just 10 percent of them are malignant.For instance, the most common type of primary cardiac tumor is called a myxoma which is generally inherited always affecting children.

References & Sources:

https://health.clevelandclinic.org/2012/11/can-you-get-heart-cancer/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4447149/

https://www.scienceabc.com/humans/why-is-there-no-heart-cancer.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3113129/

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