What is Melanoma?
Melanoma is a serious type of malignancy (cancer) that develops in cells (melanocytes) that produce melanin, the pigment that gives skin its color. Melanoma can also form in ones eyes and, rarely, in internal organs such as the intestines or rectum.
The exact cause of all melanomas is not clear, but exposure to ultraviolet (UV) radiation from sunlight or tanning lamps is a major risk factor. A risk factor is anything that increases ones chance of developing a disease, including cancer. In most cases, it appears to involve UV light radiation damage to cellular DNA. UV light does not cause all melanomas, especially those that occur in places on the body that do no receive exposure to sunlight. This indicates that other factors, including environmental and genetic factor may contribute to ones risk of melanoma.
The risk and frequency of melanoma is dramatically increasing in people under age 40, especially in women. There are about 70,000 new melanoma cases yearly in the United States and it is the main cause of death in the 20 to 30 year age group.
Hidden melanomas can also develop in areas of the body that have little or no exposure to the sun; such as spaces between the toes, or on the palms, soles, scalp or genitals. When melanoma occurs in people with darker skin, it is more likely to occur in a hidden area such as those.
Types of Melanoma
Melanoma In-Situ is the very earliest presentation of melanoma where the cancerous cells are confined to the epidermis. Most melanomas begin as In-Situ disease.
Superficial Spreading is the most common type (70% of cases). It begins in the epidermis, and grows sideways within the epidermis for a prolonged time before penetrating into the dermis, growing into deeper layers. It most often presents as a slightly raised asymmetrical lesion that is tan, black, brown, red, or purple and can appear anywhere on the body.
Nodular is almost always invasive early when it is first recognized as a bump. They are usually black but occasionally other colors. They are commonly found on the scalp in older men.
Lentigo Maligna is similar to superficial spreading and remains near the skin surface for a prolonged time. They usually are mottled tan and brown. They are In-Situ, meaning they are not invading the underlying layers. When present for a very long time they can become invasive, in which case they are known as Lentigo Maligna Melanoma.
Acral Lentiginous Melanoma also spreads on the surface for a prolonged time before penetrating the deeper layers. It usually appears as black or brown discoloration under the finger or toe nails or on the soles of the feet or palms. These tend to advance more quickly than other types. It is the most common melanoma found in African-Americans and Asians and least common in Caucasians.
As stated above, melanomas can develop anywhere on the body. However, they most often develop in areas that have been exposed to the sun such as the back, legs, arms, and face. They also can occur in areas that do not receive much sun exposure, such as the soles of the feet, palms of the hands, and fingernail beds. Again, these “hidden” melanomas are more common in people with darker skin.