What is Melanoma?
Melanoma is a type of skin cancer that forms from the melanocytes, cells in your skin that produce melanin, which is a pigment that gives your skin color. Melanocytes are located deep in the epidermis (the top layer of your skin), which is made up mostly of squamous cells and basal cells. Squamous cell and basal cell skin cancers are much more common than melanoma, but melanoma is much more dangerous and aggressive than these other forms of skin cancer. Melanomas account for only about 3% of all skin cancers, but have the highest death rate of any type, and are responsible for more than 85% of skin cancer related deaths. While rare compared to other skin cancers, the incidence of melanoma has been increasing more than any other malignancy over the last 50 years. Melanoma is now the 5th most commonly diagnosed cancer in the US, and one of the most commonly diagnosed cancers in young adults between the ages of 20 and 30. Fortunately, melanoma is very curable when diagnosed at an early stage.
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When your skin is exposed to ultraviolet (UV) radiation from the sun or tanning beds, your melanocytes produce more pigment, causing your skin to tan. Too much UV radiation can damage these cells and cause them to become malignant (cancerous) over time. Melanoma may form as a new brown, black, or red spot on your skin, or it can develop within an existing mole identified by changes in color, texture, shape, or size. A mole (nevus) is just a benign skin lesion that forms from the melanocytes. There are several different types of melanoma, each with different prognoses and treatment options.
Cutaneous Melanoma
The most common types of melanoma are cutaneous (on the skin) and are readily visible as they develop. There are several different types of cutaneous melanoma:
Superficial Spreading Melanoma
This type of melanoma can arise from a pre-existing mole. It is the most frequently diagnosed type of melanoma, and accounts for about 70% of all cases.
Nodular Melanoma
This type of melanoma is generally more aggressive as they tend to be thicker and more often ulcerated with a high mitotic rate, compared to superficial spreading melanomas. This is the second most common form, accounting for 15% to 20% of all cases.
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Lentigo Maligna Melanoma
This type of melanoma usually forms as flat, wide tumors. This form of melanoma is less aggressive and accounts for about 4% to 10% of all cases. It is most prevalent in older, light-skinned individuals often on the sun-exposed face and head and neck regions.
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Acral Lentiginous Melanoma
This type of melanoma usually arises on the palms of the hands, the soles of the feet, or under the nails, particularly in the thumb and big toe. It accounts for about 2% to 8% of melanoma cases in light-skinned people, and for about 60% of cases in dark-skinned people.
Spitzoid Melanoma
This unusual variant of melanoma is usually seen in children, adolescents, and young adults. These melanomas can be extremely difficult to diagnose, and to distinguish from their benign counterparts. Review by experienced dermatopathologist is generally recommended. These melanomas may be inherently less aggressive than conventional melanomas.
Desmoplastic Melanoma
This is another very unusual variant of melanoma, often occurring in elderly patients in sun-exposed areas. These lesions are more prone to local recurrence after excision, and less likely to spread to lymph nodes or other parts of the body than conventional melanomas. Again, the diagnosis of desmoplastic melanoma can be extremely difficult, and consultation with an expert dermatopathologist is often required.
Non-cutaneous Melanoma
Mucosal Melanoma
This type of melanoma forms in the mucosal tissues that line the inside of your body. It only accounts for about 1% of all cases and is usually very hard to diagnose and treat. Mucosal melanomas most commonly form in the tissues lining the oropharynx, anus/rectum, female genitalia, and urinary tract. They are frequently hidden from eyesight and undetected until they are large enough to cause symptoms of pain and or bleeding. As a result, these melanomas are commonly diagnosed at an advanced stage.
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Ocular Melanoma
This is another very rare type of melanoma that arises in the pigmented cells in the eye. These are diagnosed by specialized ophthalmologists, often by their appearance, and without a biopsy. Management of these lesions should be supervised in centers specializing in this unusual entity.
