Cancer, the crab of astrology, is so named because the ancients could see the abnormal cancer cells clawing their way into the normal tissue, destroying everything in their path.
Doctors now understand a great deal about cancer, but do not fully understand what starts the process. Although the specific cause of cancer is unknown in many cases, sun exposure, a low-fibre diet and smoking are well-known precipitating factors.
Cancer (malignancy or neoplasm) occurs when otherwise normal cells start multiplying at an excessive rate, and the cells made by the rapid process of reproduction are abnormal in shape, size and function.
Although they may have some slight resemblance to the cells around them, cancer cells cannot perform the correct work of that type of cell, and they prevent the normal cells around them from working properly, thus enabling the cancerous cells to spread.
Cancer is not just one disease process – dozens of different types of cancer occur in different parts of the body, and each type causes different problems and responds differently to treatment. Several different types of cancer can be found in the lungs for example.
There are however two main groups of cancers according to the type of tissue affected :-
- Sarcomas are tumours originating in connective tissue (bone, cartilage, muscle and fibre).
- Carcinomas are tumours originating in the epithelial cells (tissue comprising the external and internal linings of the body).
As a side curiosity, sharks never develop cancer, and medical scientists are still trying to work out why.
Types of Cancers