40 years ago, the world lost a legend when reggae artist Bob Marley died after a four-year struggle with a melanoma skin cancer that started on his toe.
This may seem unusual, as melanoma is usually linked to patients with fair skin and constant exposure to UV radiation from the sun. But the No Woman, No Cry singer was diagnosed with a rare but fast-growing type of skin cancer known as acral melanoma, which isn’t strongly correlated to UV exposure.
What is melanoma?
The American Cancer Society describes melanoma as a type of skin cancer that develops when melanocytes (the cells that give the skin its tan or brown color) start to grow out of control.
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can then spread to other areas of the body.
Melanoma is much less common than some other types of skin cancers. But melanoma is more dangerous because it’s much more likely to spread to other parts of the body if not caught and treated early.
How does the cancer start?
Per the American Cancer Society, most skin cancers start in the top layer of skin, called the epidermis. There are 3 main types of cells in this layer:
- Squamous cells: These are flat cells in the upper (outer) part of the epidermis, which are constantly shed as new ones form.
- Basal cells: These cells are in the lower part of the epidermis, called the basal cell layer. These cells constantly divide to form new cells to replace the squamous cells that wear off the skin’s surface. As these cells move up in the epidermis, they get flatter, eventually becoming squamous cells.
- Melanocytes: These are the cells that can become melanoma. They normally make a brown pigment called melanin, which gives the skin its tan or brown color. Melanin protects the deeper layers of the skin from some of the harmful effects of the sun.
- The epidermis is separated from the deeper layers of skin by the basement membrane. When skin cancer becomes more advanced, it generally grows through this barrier and into the deeper layers.
What are the risk factors?
Exposure to ultraviolet (UV) rays is a major risk factor for most melanomas. Sunlight is the main source of UV rays. Tanning beds and sun lamps are also sources of UV rays.
UV rays damage the DNA (genes) inside skin cells. Skin cancers can begin when this damage affects the DNA of genes that control skin cell growth.
A mole (also known as a nevus) is a benign (non-cancerous) pigmented tumor, and they usually appear as we develop through and are not born with them.
Atypical moles (dysplastic nevi): These moles look a little like normal moles but also have some features of melanoma. They are often larger than other moles and have an abnormal shape or color. (See Signs and Symptoms of Melanoma Skin Cancer for descriptions of how moles and melanomas look.) They can appear on skin that is exposed to the sun as well as skin that is usually covered, such as on the buttocks or scalp.
Family history of skin cancer
Genetics definitely plays a role in your susceptibility to skin cancer.