An overview of Melanoma

About Melanoma

Source: www.cancerfacts.com

This informattion is for educational purposes only.
Healthy cells in the body normally reproduce themselves in a controlled, orderly manner. Cancer cells reproduce themselves abnormally, dividing uncontrollably and usually more rapidly than healthy cells. They infiltrate and destroy surrounding tissue. They do not die the way normal cells do. As the cancerous cells produce more cells, a mass or a tumor may appear. As the tumor invades the surrounding tissue, it may prevent the healthy tissue from doing its normal job.

There are two kinds of tumors:
Benign tumors are usually not life threatening. In many cases, they do not invade surrounding tissue and can be removed without regrowth.




Malignant tumors are cancerous. These tumors contain cells that divide and grow without order. The cells will invade and take over nearby tissues. They can spread (metastasize) to other organs by traveling through the body's bloodstream or lymphatic system. The lymphatic system is part of the immune system. It is made up of a network of glands, called lymph nodes, and vessels that connect them. Once metastasized a tumor will invade and take over organs, interfering with their normal function.
Melanoma is a malignant tumor. It is one of three main types of skin cancer, which also includes squamous cell carcinoma and basal cell carcinoma. Squamous cell carcinoma and basal cell carcinoma are the most common forms of skin cancer, but melanoma is the most serious form. Melanoma (also called malignant melanoma) is the term used to describe cancer of the melanocytes, which are microscopic cells within the skin that normally carry melanin. Melanin is a pigment (color) that gives color to hair and skin. Its production within the skin is normally increased when skin is exposed to sunlight, which causes tanning of the skin. Large accumulations of healthy melanocytes in the skin are called freckles or moles.

When the melanocytes become cancerous (malignant), they begin to grow in a wild and disorganized fashion, eventually becoming a tumor within the skin.

Risk

In the past several decades, the risk of developing melanoma has risen dramatically. In 1935, one in 1,500 Americans developed melanoma. According to the National Comprehensive Cancer Network, for someone born in the United States in the years 2002-2004, the risk was as high as 1 in 61 for women and 1 in 41 for men. Overall, melanoma is the fifth most common cancer in young and middle-aged adults. While it can affect people of all ages, the average age at time of diagnosis is 45-55. Melanoma can occur in any population or race, though it is most common in those with fair complexion(s) and hair color, with blue or green eye color. It also occurs most frequently in those whose skin tends to burn instead of tan in sunlight, and has been linked to blistering sunburns early in life, during childhood or adolescence. Melanoma is also seen more frequently in people who have large numbers of moles.

Melanoma accounts for about 4% of skin cancer cases, but it causes about 79% of skin cancer deaths. The number of new cases of melanoma in the United States is on the rise. The American Cancer Society estimates that in 2009 there will be 68,720 new cases of melanoma in this country. About 8,650 people will die of this disease. (ACS Cancer Facts & Figures, 2009)

Survival

Although skin cancer is the most common type of cancer, only 4 percent of skin cancers are melanomas. The remaining 96 percent are squamous cell carcinomas and basal cell carcinomas. Like other skin cancers, melanoma can be cured with early detection and treatment, but unlike the other types of skin cancer, which are slow growing, melanoma can grow quickly and spread (metastasize) to other organs. It can cause a great deal of morbidity and mortality. Melanoma is responsible for 79 percent of all skin cancer deaths. When melanoma is detected and treated early, the five-year relative survival rate is greater than 99 percent. If the melanoma tumor spreads through the skin layers and to the local lymph nodes, the five-year relative survival rate drops to less than 65 percent. Once melanoma metastasizes to distant sites, the five-year relative survival rate is reduced to 15 percent. The average survival for patients with metastatic melanoma is approximately eight months. About 80% of melanomas are diagnosed at a localized stage.

Anatomy

The skin is the largest organ in your body. It helps protect the body from injury and infection, helps regulate body temperature and fluid balance, and helps generate our supply of vitamin D. In addition, this amazing organ is responsible for transmitting sensory information to your brain; the skin’s nerve endings sense temperature, texture, pressure, vibration, and pain. Skin is composed of two major layers, the epidermis and dermis.

Epidermis

The epidermis forms the thin outer layer of the skin. It is composed of two bands of cells. The upper band is formed from the flat, scaly, squamous cells that protect the lower layers of the skin. The second band lies just below and contains the round basal cells. As the scaly outer layer of squamous cells is sloughed off, the basal cells below replenish the squamous layer. Melanocytes, which contain the pigment melanin, are found in the basal cell layer and are partially responsible for giving the skin its color. If exposed to excessive sunlight, melanin makes the skin darker (“tans”) to protect the lower skin layers from ultraviolet radiation.

Dermis

The dermis forms the layer of tissue below the epidermis. It is composed of connective tissue, blood vessels, lymph channels, sweat glands, sebaceous (oil) glands, hair follicles, and nerves. This network of tissues allows the skin to serve as a sensory and temperature regulating organ.

Subcutis (Subcutaneous tissue)

Subcutis tissue lies beneath the skin and is composed of collagen and fat cells. The subcutis provides the internal organs with both insulation and protection from injury. Blood and lymphatic fluid flow through this area, through blood and lymph vessels. Blood vessels carry nutrients and oxygen to the cells, and remove waste products from the cells. Lymphatic vessels carry lymph fluid, which has many purposes, including transporting certain proteins and defense mechanisms throughout the body.



Melanoma occurs when melanocytes become cancerous (malignant) and grow in an abnormally wild and disorganized way. Melanocytes are found in the outer layer of the skin, known as the epidermis. If the cancerous Melanoma cells grow down into the deeper layers of the skin, they may invade the lymph and blood vessels and be carried to distant parts or organs of the body, where they will begin to live and grow (this is called metastasis).

Moles

Moles (also called Nevi) are benign clusters of melanocytes and are common throughout the general population. They may or may not be present at birth but are typically present in most people by early adulthood. Most people have approximately 10-20 moles. The typical mole may be flat or raised, round or oval, pink, tan, or brown, and is usually less than 5 mm (1/4 inch) in diameter. They can be found anywhere on the body. They do not itch, hurt, or bleed easily. Normal moles change or grow very little over time, and usually do not re-grow after surgical removal. Moles that differ from normal moles in shape, color, or size may be called atypical (dysplastic or not typical) moles. These moles contain abnormal melanocytes. All moles, whether typical or not, should be monitored on a regular basis for any changes in size, shape, color or easy bleeding, which could indicate a change in the melanocytes from benign to malignant. Any changes should be promptly reported to your physician. People with large numbers of moles or those with atypical or dysplastic moles should have their moles carefully monitored by their physician on a regular basis even if a change hasn't been seen, since these moles have a greater risk of becoming cancerous.

Types of Melanoma

There are three main types of skin cancer—squamous cell carcinoma, basal cell carcinoma, and melanoma. Squamous cell carcinoma and basal cell carcinoma are the most common forms, but melanoma is the most serious. The Melanoma Cancer Profiler pertains to melanoma only. Melanoma (also called malignant melanoma) is the term used to describe cancer of the melanocytes, the microscopic cells within the skin that carry the pigment, melanin. There are three primary types of melanoma.
Cutaneous melanomas begin in the skin. Although commonly found on the head and trunk in men and the lower legs in women, any skin surface can be involved. Moles are often, though not always, the original site of a cutaneous melanoma. The appearance of a melanoma can be variable, which is why all moles should be watched on a regular basis to detect any change in appearance, such as color, shape, size, or surface. Other changes could include scaling, ulceration (open wound), crusting, or bleeding. Many melanomas have no discomfort though new itching, burning, or pain should raise suspicion. Your physician should evaluate any new moles or lesions.


Ocular melanomas occur within the eye. There may or may not be any symptoms, which is one reason to undergo routine eye examinations. Symptoms of ocular melanoma may include visual changes, bulging or pain in the eye. Ocular melanomas are treated differently than cutaneous melanomas. The discussions you will find in the Melanoma Profiler Treatment Options Tool will focus on cutaneous melanomas. To find out more information on ocular melanoma, visit the choroidal melanoma page on the Eye Cancer Network website, the American Cancer Society, or consult your physician.


Other melanomas Other melanomas begin in tissues elsewhere in the body, such those with a mucus membrane lining (the digestive tract or vagina). They are very rare. These are not discussed in the Melanoma Profiler Treatment Options Tool. Obtain additional information from your physician or the American Cancer Society.



Overview of Cutaneous Melanoma

Cutaneous melanomas can appear in several different ways, though all go through the same stages of development. Initially, melanoma cells lie "in situ" ("in place") or completely contained within the epidermis. There are only a few cancer cells present at this point. As the cells begin to multiply, the cells spread horizontally through the epidermis. This is the second step of development and is called the radial growth phase. The cells are called "non-tumorigenic", meaning they have not yet formed a lump. If the malignant melanoma cells are removed early, while contained in the epidermis, complete cure can occur. Once the radial growth phase has been completed, the third step, the vertical growth phase begins. The malignant cells begin to grow deeper into the skin, invading the dermis and becoming closer to the blood and lymphatic vessels. At this stage, the cells are tumorigenic and have the potential to spread (metastasize) to other organs within the body through the lymphatic vessels. For this reason, it is important to know the depth (or thickness) of the melanoma, since the deeper its vertical growth phase, the greater the risk of metastasis, and lesser chance of cure.



In the radial growth phase, melanoma spreads horizontally through the epidermis. The cancer may then enter a vertical growth phase and invade the dermis, increasing the risk of distant spread.

Types of Cutaneous Melanoma

There are five different types of cutaneous melanoma. Distinction is made based on the location and appearance of the melanoma when it is first identified, as well as the microscopic evaluation of the tumor by the pathologist.

Superficial spreading melanoma

Superficial spreading melanoma remains the most common of the cutaneous melanomas, affecting 70 to 80 percent of all melanoma patients. It can appear anywhere on the body including areas that are not typically exposed to the sunlight, though it is most often located in areas of previous sunburn. It often, though not always, begins in a pre-existing mole, which has changed appearance as the tumor developed. It usually ranges in size from 1-2 cm (1/2-1 inch) and can have an irregular shape. It may or may not be raised from the skin surface. It is usually brown, black or tan in color, and may have pink or blue colors within it. It tends to grow slowly, compared to the other types of melanoma listed below, though faster than other skin cancers. It is the most common type of melanoma in fair-skinned races.

Nodular melanoma

Nodular melanoma occurs in approximately 10 percent of all cases of cutaneous melanoma. While it can develop anywhere on the body, it most commonly develops on the trunk. It does not resemble other forms of melanoma, as it appears as a smooth, dome shaped nodule, which often resembles a blood blister. Its color is usually blue-black, gray, or dark brown, though can also be pink or flesh-colored. It grows rapidly and tends to have a poor prognosis.

Lentigo maligna melanoma

Lentigo maligna melanoma occurs in approximately 5 percent of cases of melanoma. It develops very slowly, over several years and does not originate in a mole or nevi. It occurs in areas of the body that have had heavy sun exposure. It is usually flat with an irregular shape. It is usually greater than 1 cm (1/2 inch) and can become quite large, 3-6 cm (1 ½ -3 inches). It is colored deep tan, brown, and black.

Desmoplastic melanoma

This occurs as a firm, light-colored, nodule and is most commonly seen on severely sun-damaged skin of middle-aged to elderly men.

Acral lentiginous melanoma

This type of cutaneous melanoma occurs in 2 to 8 percent of melanomas in the Caucasian population, but is significantly more common in the African-American and Hispanic population (35-90 percent of melanomas). Sunlight exposure does not seem to play a part in its development. This melanoma begins on the palms, soles of feet, and nailbeds. It is flat, with a tan, deep brown, or black color. In the nailbeds, it can be a brown-black band within the nail, and may affect the skin near the nail. This melanoma grows and spreads very quickly, and has a poorer prognosis.

Source: www.cancerfacts.com