Overview of the Different Types of Melanoma

Melanoma, the most serious type of skin cancer, develops in the cells (melanocytes) that produce melanin—the pigment that gives your skin its color. Melanoma can also form in your eyes and, rarely, in internal organs, such as your intestines.

The exact cause of all melanomas isn’t clear, but exposure to ultraviolet (UV) radiation from sunlight or tanning lamps and beds increases your risk of developing melanoma. Limiting your exposure to UV radiation can help reduce your risk of melanoma.

The risk of melanoma seems to be increasing in people under 40, especially women. Knowing the warning signs of skin cancer can help ensure that cancerous changes are detected and treated before the cancer has spread.

Skin cancer is the most commonly diagnosed cancer in the United States. Melanoma accounts for only about 1% of skin cancers but causes a large majority of skin cancer deaths, and its incidence continues to rise at a rate faster than that of any other human cancer.

Survival rates for melanoma have improved dramatically in recent decades. The average five-year survival rate for people whose melanoma is detected and treated before it spreads to the lymph nodes is 98%. For melanomas that have spread to regional lymph nodes or to distant orgrans, the five-year survival rates are 64% and 23%, respectively.

Signs

Melanomas can develop anywhere on your body. They most often develop in areas that have had exposure to the sun, such as your back, legs, arms, and face. Melanomas can also occur in areas that don’t receive much sun exposure, such as the soles of your feet, palms of your hands and fingernail beds. These hidden melanomas are more common in people with darker skin.

The first melanoma signs and symptoms often are:

• A change in an existing mole
• The development of a new pigmented or unusual-looking growth on your skin

Melanoma doesn’t always begin as a mole. It can also occur on otherwise normal-appearing skin.

Types

There are four major types of melanoma that have distinct characteristics and potential for metastasis:

• Lentigo maligna: This type of melanoma is more commonly found on the head and neck region. It begins as a small, asymmetric pigmented patch that has irregular borders and color variations throughout the lesion. Over time the patch gets larger and retains its asymmetry, irregular borders, and color variations. This type of melanoma may remain flat and confined to the epidermis for months to many years, but at some point will penetrate into the deeper levels of skin, increasing the potential for metastases.

• Superficial spreading: This type of melanoma is more commonly found on the trunk, upper arms, and thighs, and is the most common form of melanoma in people with white skin. It begins a small pigmented macule that is asymmetric, has irregular borders, and has color variations. This type of melanoma remains in the flat phase for a shorter period of time than the lentigo maligna type before it penetrates into the deeper levels of the skin.
• Nodular: This type of melanoma can occur on any skin surface but is found more commonly on the trunk, upper arms, and thighs. The nodular type of melanoma has a very short flat phase before it forms a raised nodule and penetrates into the deeper levels of the skin. This type of melanoma may ulcerate and present as a non-healing skin ulcer.

• Acral-lentiginous: This type of melanoma is more commonly found on the hands, feet, and nail beds. It is most frequently found in dark-skinned people. It is similar to the lentigo maligna and superficial spreading type in that it has a relatively long flat phase before it penetrates into the deeper levels of the skin.