The skin has many purposes, it:
The skin is divided into three main layers: the outer layer known as the epidermis , a layer underneath known as the dermis and a deeper layer, which is made up of fatty tissue.
The epidermis contains three types of cells. Most of the epidermis is filled with cells known as squamous cells . At the base of the squamous cells are rounder cells called basal cells. In between the basal cells are other cells called melanocytes . Melanocytes are cells that produce the pigment melanin . It is this pigment that gives skin its colour variations.
The structure of the skin
What is cancer?
The organs and tissues of the body are made up of tiny building blocks called cells. Cancer is a disease of these cells.
Cells in different parts of the body may look and work differently but most reproduce themselves in the same way. Cells are constantly becoming old and dying, and new cells are produced to replace them. Normally, cells divide in an orderly and controlled manner. If for some reason the process gets out of control, the cells carry on dividing, developing into a lump which is called a tumour.
Tumours can be either benign or malignant. Cancer is the name given to a malignant tumour. Doctors can tell if a tumour is benign or malignant by examining a small sample of cells under a microscope. This is called a biopsy.
In a benign tumour the cells do not spread to other parts of the body and so are not cancerous. However, if they continue to grow at the original site, they may cause a problem by pressing on the surrounding organs.
A malignant tumour consists of cancer cells that have the ability to spread beyond the original area. If the tumour is left untreated, it may spread into and destroy surrounding tissue. Sometimes cells break away from the original (primary) cancer. They may spread to other organs in the body through the bloodstream or lymphatic system.
The lymphatic system is part of the immune system - the body's natural defence against infection and disease. It is a complex system made up of organs, such as bone marrow, the thymus, the spleen, and lymph nodes. The lymph nodes (or glands) throughout the body are connected by a network of tiny lymphatic ducts.
When the cancer cells reach a new area they may go on dividing and form a new tumour. This is known as a secondary cancer or metastasis. Even when cancer spreads somewhere else in the body, it is still the same kind of cancer, and is still named after the part of the body where it started. For example, if lung cancer spreads to the bones, it is still lung cancer, not bone cancer. In that case, it may be said that the person has "lung cancer with bone metastases."
It is important to realise that cancer is not a single disease with a single type of treatment. There are more than 200 different kinds of cancer, each with its own name and treatment.
Types of cancer
The majority of cancers, about 85% (85 in a 100), are carcinomas. They start in the epithelium, which is the covering (or lining) of organs and of the body (the skin). The common forms of breast, lung, prostate and bowel cancer are all carcinomas.
Carcinomas are named after the type of epithelial cell that they started in and the part of the body that is affected. There are four different types of epithelial cells:
A cancer that starts in squamous cells is called a squamous cell carcinoma. A cancer that starts in glandular cells is called an adenocarcinoma. Cancers that start in transitional cells are transitional cell carcinomas, and those that start in basal cells are basal cell carcinomas.
Leukaemias and lymphomas
These occur in the tissues where white blood cells (which fight infection in the body) are formed, i.e. the bone marrow and lymphatic system. Leukaemia and lymphoma are quite rare and make up about 6.5% (6.5 in 100) of all cancers.
Sarcomas are very rare. They are a group of cancers that form in the connective or supportive tissues of the body such as muscle, bone and fatty tissue. They account for less than 1% (1 in 100) of cancers.
Sarcomas are split into two main types:
Others forms of cancer
Brain tumours and other very rare forms of cancer make up the remainder of cancers.
Types of skin cancer
There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma and malignant melanoma.
Basal cell carcinoma
Basal cell carcinoma, or BCC, is a cancer of the cells at the bottom of the epidermis called the basal cells. It is very common and accounts for more than three-quarters (75%) of all skin cancers in the UK.
Each year more than 60,000 people in the UK develop BCC. Most BCCs are very slow-growing and almost never spread to other parts of the body. They often start as a small, red, shiny spot or nodule that may bleed occasionally.
In many BCCs, the skin over the top can remain intact for many months. Eventually they may develop into an ulcer which does not heal. When BCCs are treated at an early stage, most of the time they are completely cured. However, some BCCs are aggressive, and if left to grow they may spread to deeper layers in the skin and sometimes to bones, making treatment difficult. A small number of BCCs may also come back on the same area of skin after treatment – this is known as a local recurrence .
Squamous cell carcinoma
Squamous cell carcinoma, or SCC, is a cancer of the outermost cells of the skin. It's the second most common type of skin cancer in the UK. One in five skin cancers (20%) are this type.
Usually squamous cell carcinomas are slow-growing and only spread to other parts of the body if they are left untreated for a long time. But occasionally these cancers can behave more aggressively and spread at a relatively early stage. However, most people treated for squamous cell carcinoma are completely cured with simple treatment.
Another less common type of skin cancer is called malignant melanoma. About 7,000 people in the UK are diagnosed with malignant melanoma each year. Melanoma behaves differently to basal cell and squamous cell cancers. It can grow quickly and needs to be treated early.
We have separate information on malignant melanoma .
Rarer types of non-melanoma skin cancer
There are a number of other rare types of non-melanoma:
These rare types make up less than 1 in 100 of all skin cancers (1%) in the UK.
Risk factors and causes of skin cancer
Ultraviolet light (UVA and UVB) from the sun is the main environmental cause of most skin cancers. It's likely that most skin damage from ultraviolet light occurs before the age of 20, but it doesn't show up until many years later. Damage to the skin below the age of 20 is an important risk factor in the development of basal cell cancers. Sun exposure over a lifetime is more significant for squamous cell cancers.
Skin cancer is becoming more common and there are several possible reasons for this. People are living longer and so their lifetime sun exposure is greater. They often spend more time enjoying outdoor activities and holidays in sunny climates, and many people still consider suntans to be healthy and attractive. Another reason why skin cancers appear more common is because awareness has increased over the last 20 years.
People who work outdoors for a living, such as farm workers, builders and gardeners, are at an increased risk of developing skin cancer because of prolonged exposure to the sun. This is relevant for both squamous cell and basal cell cancers.
Black- or brown-skinned people have an extremely low risk of developing skin cancer because the melanin pigment in their skin gives them protection. A fair-skinned person who tends to go red or freckle in the sun will be most at risk. Children and young adults who have been overexposed to the sun have an increased risk of developing some form of skin cancer especially if they are fair skinned. This will not show up until later on in life – usually after about the age of 40, and often not until the age of 60 or 70.
The regular use of sunlamps and sunbeds can increase the risk of developing some skin cancers but this is seen mainly in people who have used them excessively and regularly for many years.
Previous radiotherapy treatment
Radiotherapy given to treat other conditions can sometimes cause skin cancers, particularly basal cell cancers, in the treatment area later in life.
People who have to take drugs that lower their immunity (immunosupressants) – for example, after a kidney transplant – are at an increased risk of getting skin cancer. Squamous cell cancers are most frequent but basal cell cancers and melanomas are also more common in these people than in the general population.
However, the reason for taking the immunosuppressants outweighs the potential risk of skin cancer. If you've had a transplant it's important that you see your doctor regularly to check for early signs of skin cancer.
Exposure to chemicals
Another rare possible cause for non-melanoma skin cancer is overexposure to certain chemicals at work. These include:
You should wear protective clothing if you are handling these substances frequently. Very small amounts of these chemicals used in the home are unlikely to cause skin cancer but you should follow the manufacturer's instructions for their use.
Most skin cancers are not caused by an inherited faulty gene that can be passed on to other family members, so members of your family are not likely to have an increased risk of developing it. However, families are likely to have the same skin type, which may increase their risk of developing a skin cancer.
People with certain rare hereditary conditions, such as Gorlin's syndrome or xeroderma pigmentosum (XP), have a higher risk of developing skin cancer.
How common is the Skin Cancer in India?
Skin cancer is one of the rare cancers diagnosed in India. It ranks lower than number 15 among all other cancers for people from the Indian subcontinent1.
In India, between the years 2001-2003, across five urban centers - Mumbai, Delhi, Chennai, Bhopal and Bangalore, – and one rural center - Barshi, a total of 709 cases of Melanoma and other types of skin cancers were registered (1.60% of all cancers) for males across all age groups; while 479 cases of Melanoma and other types of skin cancers were registered (1.08% of all cancers) for females across all age groups. Considering all men, women and children with all types of cancers together, a grand total of 1,188 cases of Melanoma and other types of skin cancers (1.34% of all cancers) were registered at the six centers mentioned above, between the year 2001-20032.
The TATA Memorial Hospital (T.M.H.) in Mumbai, India registered a grand-total of 19,127 cases of all types of cancer patients in the year 2006 for men, women and children combined, out of which 60 (0.3% of the total cases) were diagnosed with the Melanoma of the skin, which is the major type of skin cancer in India. Out of the total 60 patients diagnosed with Melanoma of the skin, mentioned above at the T.M.H., 41 (68%) were males and 19 (32%) were females3.
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