Xeroderma pigmentosum

Skin cancer is the uncontrolled growth of cells within the skin.  There are 3 main types of skin cancer depending on the type of cell where the tumour originates:

• Basal cell carcinoma
• Squamous cell carcinoma
• Malignant melanoma

As its own names indicate, basal cell carcinoma involves cells in the basal layer of the epidermis where the keratinocytes start differentiating and it is the most common type of skin cancer. They usually are slow-growing tumours that rarely metastasize to long distances in the body. Squamous cell carcinomas, the second most common type of skin cancer, are tumours originated in the squamous keratinocytes that form the squamous layers, when the cells are flattened and forming multiple layers to form the physical barrier, main function of the skin. Finally, the most aggressive form of skin cancer, melanoma, originates in the melanocytes present in the basal layer. These tumours are generally brown or black in colour because the cells still make melanin, but they can also be skin-coloured, pink or white. They usually grow vertically, invading the dermis, being more promptly to produce metastasis.

The deeper a cancer cell grows into the dermis, the higher the risk of spreading through lymph vessels and blood vessels and having relapses over extended periods of time. This is why finding skin cancer as early as possible is so important. However, most of skin cancers can be treated or even removed by surgery if they are found early before they have spread.