WHAT IS MELANOMA?
Melanoma is cancer arising from melanocytes, which are the pigment producing cells of the skin. The skin has two layers:
1) the epidermis which contains skin cells (keratinocytes) and
2) the dermis which contains the hair follicles, glands and structures that give the skin it’s strength.
How strong is the dermis – well our factories make belts, shoes and other products form the dermis of animals. Your dermis is very strong and does not tear easily. In normal skin, the melanocytes are located in the lower layer of the epidermis. In melanoma, when the cancerous cells are contained within the epidermis this is considered “in situ”, meaning that it has not spread to affect the other layers or structures of the skin. When the melanoma invades beyond the epidermis into deeper skin structures such as the dermis, this is considered “invasive” and because the dermis is rich in blood and lymphatic vessels, invasive melanoma has the potential to spread beyond the skin to lymph nodes and other organs.
WHAT DETERMINES SKIN COLOUR?A person’s natural skin colour is largely a result of their genetics. All colours of skin have the same number of pigment producing cells, called melanocytes. However, the melanocytes in people with darker skin colour make more pigment, called melanin. Melanocytes are found in the layer of the skin called the epidermis, which is the outer most layer. The epidermis serves an important role in protecting the lower skin layer, called the dermis, and the tissues inside the body from harm and the outside world. Epidermis really works as a barrier not allowing water to leave or harmful substances or germs to enter. When someone has an “erosion” of the skin – the epidermis is damaged and the skin looks denuded as the underlying dermis is exposed. Melanin acts as our body’s defense against the harmful and cancer-causing ultraviolet (UVA and UVB) rays from the sun. Although people with darker skin have more protection against these harmful rays naturally, they are still susceptible to certain types of skin cancers, including melanoma. It is estimated that darkly pigmented skin provides a natural SPF protection of ~13.4. However, to best protect skin from accelerated aging and cancer, an SPF 30 or higher is recommended.
WHAT ARE THE SIGNS AND SYMPTOMS OF MELANOMA?
SUPERFICIAL SPREADING MELANOMA
The superficial spreading type of melanoma represents 70% of melanomas, making it the most common type of melanoma. It is typically seen between the ages of 30 and 50 years old. This type of melanoma most classically fits the “ABCDE” criteria of melanoma. These criteria are used to identify features that are concerning for melanoma. These are not diagnostic criteria, but they are helpful signs to look for, when you do a home skin examination.
THE “ABCDE” CRITERIA OF MELANOMA.
If you were to draw a line down the center of a spot, if the two sides aren’t a mirror image of each other this is concerning for melanoma. Round or oval shapes of moles are reassuring.
The borders of melanomas tend to be irregular, with a notched appearance rather than the smooth round lines seen in moles. If a mole looks like a map of a country– it is suspicious.
If there are multiple colors present within a mole this could be a warning sign. Possible colours include shades of brown, black, blue, white, grey, or red. Also, some melanomas can completely loose their pigment and appear as flesh color or wart like skin bumps. If you are concerned, it is best to verify with a certified dermatologist.
Diameter and ugly Duckling. Most melanomas are greater than 6mm, which is approximately the size of the erasers on the ends of pencils. Additionally, if one mole sticks out and looks different than those around it or elsewhere on your body this is called the “ugly duckling” sign and is a worrisome feature for melanoma.
This is the most important sign. If you notice that a mole is changing in size, shape, colour over time, or starts to develop new symptoms such as bleeding, crusting or pain, it could be a warning sign for melanoma.
Nodular melanoma is the second most common type of melanoma, making up 15-30% of all melanomas. It typically presents as a rapidly growing black or blue bump on the skin that can bleed. While it can occur on any body site, it is most common on the trunk, head and neck. Nodular melanoma is more frequently seen in men and is most common in sixties and seventies. We estimate that 5-10% of nodular melanomas may actually lose their pigments (appear as “amelanotic” or flesh color). Unfortunately, it is associated with worse prognosis because melanoma cells grow deeper into the skin right away without having a horizontal growth phase like in the superficial spreading type of melanoma. It is important to show any new growing and bleeding/crusting mole to a dermatologist as soon as possible.
Lentigo maligna melanoma is a less common type of melanoma, making up just 10% of all melanomas. Clinically it tends to be flat and brown with irregular borders. It is most commonly seen in older people, with the typical age of diagnosis being in the seventies or later. They are most commonly found on the face, especially the nose and cheek. While dermatologists believe that nodular and superficial melanomas arise due to intermittent sun exposure (like getting a sun burn during a vacation), the lentigo maligna melanomas happen due to chronic sun exposure – not protecting your skin from the sun for years and decades.
ACRAL MELANOMA/ACRAL LENTIGINOUS MELANOMA
Acral melanomas are typically found on the palms, soles and other extremities or around the nails. They are most frequently diagnosed in the 7th decade of life and are the most common type of melanoma in darker skinned individuals. They represent just 5% of all melanomas. If you see a black streak on your nail (called linear melanonychia) – it is best to get it checked by a certified dermatologist.