Cancer is one of the most dangerous diseases in the entirety of recorded human history. It is the second leading cause of death in the world today. In 2018, 9.6 million people died from cancer related diseases - constituting one in every six deaths. To put things into perspective, the number of death by terrorist groups in 2017 was less than 19,000, which means, it would take 500 years for the number to equal the number of deaths caused by cancer.

The mortality rate of cancer differs depending on the variant. Certain variants, such as prostate and thyroid cancer, are very manageable, and have survival rates of over 98%. On the other hand, variants such as glioblastoma will inevitably lead to death, with the majority of patients dying within 15 months of diagnosis.

What is cancer?

Cancer, which is sometimes referred to as malignant neoplasm, is an umbrella term for a group of diseases which are caused by unexpected changes of the body’s cellular characteristics. There are well over 200 different types of cancer which can affect practically every part of the human body.

The human body, like other lifeforms, is comprised of billions of cells. Typically, the development of cells in the body is tightly regulated by a variety of factors. The body, using codes supplied by genes and proteins as raw materials, grow and divide specialized cells which are then deployed in areas like the skin, brain, liver, blood cells, etc.

However, due to a combination of factors, some humans generate atypical cells with ambiguous or faulty functions. As a result, these cells will grow and divide uncontrollably in the same location. Furthermore, these rogue cells are not encoded with apoptosis, or programmed death, unlike normal cells, which have a finite lifespan. In the absence of self-destruct signals, the cells will ‘live’ until they are extracted or the host body dies.

Over time, the accumulation of cells will lead to the formation of tumours (or seep into blood vessels), which will then start to negatively affect existing ecosystems in their microenvironments. Some of the more common impacts include siphoning nutrients and oxygen from delivery systems, blocking blood vessels, compressing internal organs and destroying internal structures.

Since cancerous cells are native to the body, they are not attacked by the immune system. Consequently, they will spread through the lymph nodes, which will then conceivably lead to metastasis, or the formation of new tumours in other locations. Left unchecked, this will result in death.

Chief causes of cancer

In contrast to a majority of diseases, cancer cannot be attributed to a singular factor. Instead, genetic mutations triggering the emergence of cancerous cells are caused by a combination of genetic, lifestyle and environmental factors, which includes, but are not limited to:

• Smoking (a factor in 20% to 25% of cancer deaths)
• Inherited genetic defects (5% to 10%)
• Diet (30% to 35%)
• Radiation (5% to 10%)
• Foreign infections (15% to 20%)
• Alcohol (4% to 6%)
• Environmental pollution (5% to 10%)
• Obesity (7.8%)
• Age (87% of cancer cases involve people age 50 years and older)

Most common types of cancer

Although cancer can manifest in a variety forms and locations, some types of cancer are more prevalent compared to the rest. A study by the World Cancer Research Fund identified the following ten variants as the most common among the 17 million cases of cancer detected in 2018 (not including non-melanoma skin cancer).

1. Lung: 12.3 % (2,093,876 cases) – affects the cells within the lining of the lungs
2. Breast: 12.3% (2,088,849) – the most common among women
3. Colorectal: 10.6% (1,800,977) – include both colon and rectal cancers
4. Prostate: 7.5% (1,276,106) – the most common among men
5. Stomach: 6.1% (1,033,701) – manifest within the lining of the stomach
6. Liver: 5.0% (841,080) – Symptoms include the swelling of the liver and spleen
7. Oesophagus: 3.4% (572,034) – vertical tube connecting the mouth to the stomach
8. Cervix uteri: 3.3% (569,847) – chiefly caused by HPV (human papillomavirus)
9. Thyroid: 3.3% (567,233) - a gland located at the base of the neck below the Adam's apple
10. Bladder: 3.2% (549,393) – the symptoms include orange or pink colour urine

Rare and obscure forms of cancer

Cancer has thankfully received the attention it deserved over the past few decades. However, the medical community and mainstream media tend to focus only on the most common ones. But what about the rarer ones, which afflicts fewer than two in 100,000 people? Please continue reading the following pages to learn about some of the lesser known forms of cancer.