Skin is the largest organ of the body and has various components to it and globally most prevalent (40%). Hence, skin cancer is one that arises from skin cells and can be of different kinds:
- Melanoma: Cancer of melanocytes( Forms pigment)
- Basal cell carcinoma: Cancer of lower part of epidermis
- Squamous cell carcinoma: Cancer of squamous cells( flat cells that form the surface)
- Neuroendocrine carcinoma: Cancer of cells that release hormones to nervous system
More than 90% of the cases are a result of Ultra-violet rays exposure and weekend immunity due to old age. One can limit chances of skin cancer by reducing exposure to UV rays. Keeping a check on skin for any kind of major /minor changes may help in early detection and giving a good prognosis. 
Risk factors of Skin Cancer
Your skin colour is one of the major risk factor that can contribute to your chances of having skin cancer. Different types have different prevalence in population, e.g. Basal Cell carcinoma has highest chance of occurrence in Caucasians, Hispanics, Chinese, and Japanese Asians.
Exposure to Ultra-voilet rays ( A and B), Sunburn, Tanning salons, carcinogen, immunosuppressive agents and Ionizing radiation can be among few other causes.
HPV (Human Papilloma Virus) is also known to cause some kinds of skin cancers. 
Signs and symptoms of Skin Cancer
Any change in the skin that persists for a longer duration than usual should be a cause of concern and make you book an appoint with your GP/Dermatologist. Different types exhibit different variety of symptoms.
Melanoma can occur anywhere in the body irrespective of exposure to sun and skin colour .It can occur anywhere on a normal skin or involving a mole.
Melanoma signs include:
- Darker speckles with large blackish-brownish spot
- A pre-existing or a new mole that shows a variation in colour or grows suddenly, bleeds or feels different
- Irregular border of lesion and varying in colours
- Dark lesions on your extremities like hands, feet, fingers, or on mucous membranes of your mouth, nasal tract and anus
Basal Cell Carcinoma
Mainly occurs in the area of skin that are exposed to sun.
They are flat, flesh coloured or brown coloured lesion and may appear pearly or waxy bump.
Squamous Cell Carcinoma
Darker skins are more affected with a tendency of appearance on skin exposed area as well as non exposed
It may appear as a firm red nodule or a flat, crusted surface. 
Tests and Diagnosis of Skin Cancer
Physical examination is still the gold standard to examine any changes in the skin. If any new lesion/mole/nodule looks suspicious, a sample is taken and sent for biopsy. Biopsy helps determining the characteristics of the cancer and helps in staging of cancer on a scale of I to IV.
Staging cancer further helps the physician to choose the right course of treatment for you.
Treatment of Skin Cancer
Treatment mainly depends on staging and characteristics like size, type, depth of the lesion.
Various treatment options available are:
- Freezing. Liquid nitrogen is used to freeze and destroy acnitic keratoses as well as skin cancers in early stages. The dead tissue later goes away.
- Excisional surgery. Used for any variant of skin cancer. With a wide excision, your doctor will take the cancerous tissue and some healthy tissue to ensure no cancer cells are left behind.
- Mohs surgery. Treatment of choice for basal and squamous cell carcinomas which are large, apper again and again or are difficult to treat. Preferred treatment of choice where you want to conserve original skin as much as possible such as nose.
- Curettage and electrodesiccation or cryotherapy. After removing most of the cancerous cells, a circular blade is used to remove layers of cancer cells. Remainder of cancer cells are destroyed by electric needle.
- Some other procedures which are comparatively quick, may be used to treat basal cell cancers or thin squamous cell cancers are:
- Radiation therapy. High-powered energy beams, are used to kill cancer cells. Used when all of the cancer cannot be removed in the surgery.
- Chemotherapy. When drugs are used to target and kill cancer cells its called chemotherapy. For, superficial cancers, topical treatment is used, but when cancer has spread to body, systemic chemotherapy is used.
- Photodynamic therapy. A combination of laser with drugs that destroys cancer cells by making it sensitive to light.
- Biological therapy. Cancer cells grow due to low immune response. So by increasing your immune response your cancer cells are killed.