What is cancer?
Cancer (from the Latin for crab) is a group of diseases in which cells grow uncontrollably and have the ability to spread to another part of the body. There are more than 200 different cancers and each type of cancer has its own characteristics. When a cancer spreads to another part of the body it takes its own characteristics with it. So, for example, if a renal cancer spread to the liver, the tumour in the liver would both look and behave the same way as the original tumour. Cancer cells develop as a result of damage to DNA, the controlling mechanism for all the activities of the cells. This damage may be caused by a number of factors, including environmental, dietary and genetic. The body normally repairs damaged DNA, but in cancer cells this does not occur.
Cancers originate from a single cell. This cell divides and eventually forms a tumour. Tumours can be either malignant or benign.
Malignant tumours are cancerous tumours. The rate of cell division in cancer cells is greater than the rate of cell death, resulting in the growth of a tumour. Cancers do not always grow particularly fast. It is actually the lack of cell death in cancers that causes them to grow, rather than cell division being particularly fast. Cancerous tumours can originate in any of the common tissue types in the body.
Another important characteristic of cancer cells is their inability to recognise when they come into contact with different cell types. This means they are able to spread away into surrounding tissue and other areas of the body, via the blood stream or the lymphatic system (metastasise).
Benign tumours are not classified as cancers. The main difference between benign and malignant (cancerous) tumours is that benign tumours do not spread away from the site of origin.
Types of kidney cancer
The most common form of kidney cancer is renal cell carcinoma or RCC for short. About 90 per cent of kidney cancers are RCCs. There are several different sub-types of RCC, which are named according to the type of cell that is affected, or the appearance of the cancer cells under the microscope. The most common of these is clear cell, which account for about 75 per cent of RCCs. Other subtypes include papillary, chromophobe, and collecting duct carcinoma.
Subtypes of renal cell carcinoma (RCC):
- Conventional or clear cell RCC – this can also be called non-papillary RCC and accounts for 75 per cent of RCC cases. The cancer cells appear clear under the microscope and have large nuclei.
- Papillary or chromophilic RCC accounts for about 10-15 per cent of RCC cases. The tumours have characteristic papillae or nodules on the surface.
- Chromophobe RCC accounts for about 5 per cent of cases
- Collecting duct carcinoma
- Renal medullary carcinoma
- Mucinous tubular and spindle-cell carcinoma
- Renal translocation carcinomas
- Unclassified RCC, the latter five of which together make up the remaining 5-10 per cent of RCC tumours