Cancer forms because of a defect in the mechanism that controls the replication of cells. Certain molecules control your cells, called DNA, that are found within their nuclei. This DNA codes information that is necessary for the cell to make different molecules or proteins that, in turn, control the cell’s functioning.
Some cells of our body keep getting renewed, such as the skin. They usually have a basal layer that keeps giving out newer cells regularly. This kind of cell is present not just in the skin but also lining of different organs in the body. This is known as epithelial or endothelial tissue if it is on the inside surface of organs. These cells replicate very fast and are controlled by intricate mechanisms guiding them on when they need to replicate and when to stop replicating.
The DNA becomes exposed when a cell replicates, which can cause changes in its structure, known as mutations. These mutations may affect the mechanism that controls cell replication, eventually leading to cancer. Since there are multiple mechanisms controlling the growth of cells, it is when multiple protective mechanisms break down that a cell becomes genuinely cancerous.
Some mutations in the genes or defects in the genes are already present in our cells. However, the protective mechanism may completely break down if another mutation is caused by environmental factors or exposure to carcinogens, such as dangerous chemicals or radiation.
Our heart is one of the few organs which does not contain a layer of epithelial or glandular cells. Some of the muscle cells in our heart exist throughout life, and the other cells are from connective tissue that makes up the heart's structure and does not replicate as quickly. Because the cells do not reproduce as soon, they are less exposed to the chances of mutation. Since cancer development is linked to the fast replication of cells, the chances of cancer manifesting in the heart are reduced.
There is also the advantage that the heart does not come in contact with any environmental factor and is, consequently, less exposed to carcinogens.
However, cancers that start in other areas, such as nearby organs like the lungs and breast, can affect the heart or its covering, known as the pericardium. Cancers may also spread through the bloodstream, get deposited, and start growing in the heart.