Skin Cancer: Malignant Melanoma Diagnosis

  • Diagnosis

    Malignant melanoma is a skin cancer that is becoming increasingly common worldwide. Although it is often deadly, it can be cured if caught in its earliest stages. Malignant melanoma, also known simply as melanoma, is the sixth most common cancer in the U.S., and is the cancer increasing most rapidly worldwide. The estimated lifetime risk for melanoma has skyrocketed from 1 person in 1,500 for those born in 1935 to 1 in 75 for those born in the year 2000. Like other types of skin cancers, malignant melanoma is closely associated with excessive sun exposure, although genetic susceptibility is also a factor. People with light skin who sunburn easily are at the highest risk, but darker-skinned individuals can also develop melanoma.

    Malignant melanoma, while not as common as the nonmelanoma skin cancers, is the most deadly form of skin cancer. Malignant melanoma can arise from a pre-existing mole, or from normal skin. It often appears as an unusual, odd-shaped lesion, with irregular shape or color. The thicker the lesion, the greater the chances are that it has already spread (metastasized) to lymph nodes and distant sites. At this point, prospects for long-term survival tend to be poor.

    However, cure rates are high if the lesion is discovered and removed in its earliest stage. A variety of new treatments are currently being tested for this feared disease, which often strikes adults in the prime of life.

    Melanoma can occur in people of all races, but is much less common in dark-skinned individuals.

    Melanoma is predominantly associated with excessive sun exposure, but can also arise in areas of the body protected from sunlight. Like all skin cancers, malignant melanoma is most common in fair-complexioned individuals who have a history of bad sunburns and chronic sun exposure. It also tends to run in some families with a recognized gene mutation, which seems to confer increased susceptibility to the disease.

    For unknown reasons, a small percentage of melanomas occur on areas that are normally protected from sunlight, such as the palms of the hands, the soles of the feet, or under the nails.

    Melanoma originates from cells that are actually supposed to protect our skin from sunlight (melanocytes). Melanoma develops from melanocytes, cells that contain melanin, the pigmented chemical that protects our skin from sunlight. Melanocytes are located in the deepest (or basal) layer of the outermost layer of the skin (epidermis). Early melanomas may grow slowly, and only on the surface of the skin for a period of months or several years. Later, lesions tend to get thicker and grow deeper into the skin. Melanoma then tends to grow aggressively, and spreads to distant sites. The cancer cells spread to lymph nodes in the area, and through the bloodstream to the liver, lungs, bones, and brain.

    Malignant melanoma should be suspected if there is a change in an existing mole, or if a new mole-like lesion develops. Irregularities in shape or color are hallmarks of a melanoma lesion Figure 01. Although lesions of malignant melanoma can arise anywhere on the body, they most commonly develop on the upper back of both men and women, and on the legs of women.

    You can tell the difference between a normal mole and one that could be more dangerous by using the “ABCDE” rule. The letters A, B, C, D, and E stand for different aspects of mole appearance that serve as warning signs that your mole may be cancerous.

    • A is for asymmetry. See a doctor if your mole has an uneven shape, as opposed to an even, round, or oval shape.
    • B is for border. See a doctor if your mole has a jagged or ill-defined border.
    • C is for color. See a doctor if your mole has many colors, of if the color is not uniform.
    • D is for diameter. See a doctor if you have a mole that is larger than 6 mm (.24 inches, or about the size of a pencil eraser).

    E is for enlargement. See your doctor for a mole that has gotten larger.

    Later features of melanoma include an increase in height of the lesion, as well as crusting, bleeding, or pain.

    Occasionally melanomas may lack pigment, or may lack the ABCD features.

    Click to enlarge: Malignant Melanoma

    Figure 01. Malignant Melanoma

    Most cases of malignant melanoma occur in light-skinned individuals who have had excessive sun exposure. Other risk factors are excessive exposure to ultraviolet (UV) radiation, the presence of a giant birthmark or multiple moles, family history of melanoma, and a previous diagnosis of melanoma. Those who have had excessive exposure to ultraviolet (UV) radiation are particularly at risk, including those who suffered severe sunburns in childhood and adolescence, and people who underwent long-term UV light-based therapy (PUVA) for their psoriasis.

    People who burn easily are most susceptible; especially individuals with freckles, blond or red hair, and blue or gray eyes. Individuals with multiple moles also have an increased risk. While other skin cancers tend to occur in the elderly population after a lifetime of accumulated sun exposure, melanoma is becoming increasingly common in younger people: 25% of tumors occur in patients younger than age 40.

    Blacks are less likely to get melanoma than whites, but when they do, the cancer tends to be more aggressive, and mortality rates are increased. Dark-skinned individuals tend to get melanoma in places that are not exposed to the sun, including the palms of the hands, soles of the feet, mucous membranes, and under the nails.

    Some genetic factors have been identified that increase susceptibility to melanoma. Family members of melanoma patients are deemed to be at higher risk. Large, congenital birthmarks(>8 inches, or about the size of an adult hand) are clearly associated with an increased risk. While malignant melanoma is rare in children, about half the cases that do occur in childhood arise from these giant birthmarks. The risk connected with smaller congenital moles is more controversial, and some doctors recommend monitoring them carefully rather than removing them.

    People with the genetic condition known as atypical mole syndrome have numerous atypical moles, and tend to develop melanoma at a younger age. Atypical moles have an irregular surface, a mixture of colors, and ill-defined borders.

    People who have had malignant melanoma once are at increased risk for developing a second primary tumor later in their lives. A primary tumor is the beginning site of a cancer, in contrast to secondary sites that become cancerous as the result of the cancer spreading.

    Melanoma is suspected from the appearance of a lesion, but cells need to be examined microscopically to confirm the diagnosis. In addition, evaluation of nearby lymph nodes helps determine treatment and prognosis. A melanoma may start with an existing mole or birthmark, or from a site that was previously undistinguishable from the surrounding tissue. Seventy-five percent of such tumors then undergo progressive change over a period of six months to as long as many years, during which time the malignancy develops, but may not spread (metastasize) to other sites in the body. Because early detection greatly improves the outcome of a patient with melanoma, a primary care provider will check moles and other suspicious growths for changes indicating melanoma (e.g., sudden growth, changes in color or change to multiple colors, and irregular shape) during a routine physical examination. Individuals at risk for melanoma should ask their primary care provider to show them how to perform a self-examination. About half of melanomas are discovered through self-examination. People who are at high risk of developing the disease should consider yearly examinations by a dermatologist.

    If melanoma is suspected, the patient's primary care provider may refer the patient to a dermatologist who is trained in recognizing the earliest signs of a melanoma lesion. The dermatologist will perform a biopsy on suspicious lesions. During a biopsy, the doctor removes the tissue suspected of containing a melanoma (often a mole and a bit of the skin around it), and examines the tissue under a microscope. Usually the entire lesion is removed for a biopsy, although it is also possible to just remove a portion of it for examination. A biopsy is typically an outpatient procedure, performed in the doctor's office with only a local anesthesia. If the physician feels certain that all malignant tissue was removed at the time of the biopsy, and that no enlarged lymph nodes are detectable, he or she may advocate a “wait-and-see” approach with regular follow-up to monitor any change.

    If the biopsy examination confirms the presence of cancer, your lymph nodes may be biopsied to search for cancer cells regardless of whether or not the nodes are enlarged. The standard lymph node biopsy is referred to as a dissection, and involves opening up the area, removing multiple nodes, and checking them for cancer. In recent years, however, doctors have experimented with taking out just one or a few nodes to search for cancer. This “sentinel node biopsy” has fewer side effects than a standard lymph node dissection. It remains to be proven whether long-term survival rates are improved by sentinel node biopsy.

    The sentinel node is believed to be the lymph node that is the first “filter” for lymphatic fluid that comes from the tumor. Doctors find this node by injecting either a small amount of a radioactive substance or a blue dye at the site of the melanoma, then monitoring which lymph node or nodes collect the tracer material. The implicated node or nodes are removed, and, if cancer is detected, a standard lymph node dissection is carried out. If not, no further surgery is done.

    If there are no signs that the cancer has spread beyond the tumor site, most doctors perform at least a chest x-ray to see if cancer has spread to the lungs. If a doctor is more suspicious of advanced disease, CT, MRI, or nuclear scans of the chest, head, abdomen, and pelvis may also be ordered. Doctors also check the skin thoroughly for any sign of a second primary melanoma lesion.

    If the cancer has spread, the doctor, usually either a dermatologist who specializes in skin cancer, or an oncologist, a doctor who specializes in the treatment of cancer, will “stage” it. There are several staging systems; one of the most common assigns the cancer a number, I through IV, based on the size of the tumor and the degree to which it has spread.

    • Stage I: The tumor is in the outer layer of the skin (epidermis), and may have reached the upper part of the dermis (the inner layer of skin), but no further. The lesion is less than one sixteenth of an inch thick (a little less than the thickness of a penny).
    • Stage II: The tumor has spread to the lower part of the dermis, but not into the surrounding tissue or lymph nodes. The lesion is less than one-sixth of an inch thick (a little less than the thickness of two quarters).
    • Stage III: The tumor has any one of the following characteristics: it is more than one-sixth of an inch thick, it has spread to the tissue under the skin, there are other tumors growing within one inch of the origin tumor, or the tumor has spread to nearby lymph nodes.
    • Stage IV: The tumor has spread to other organs or lymph nodes distant from the original tumor site.

    Protection from excessive sun exposure—especially though frequent use of sunscreen with SPF 15 or higher, protective clothing, and avoiding the midday sun—is essential for reducing the risk of all types of skin cancer. Light-skinned individuals who burn easily should be especially cautious. The following precautions should be taken by everyone to guard against excessive exposure to UVA and UVB radiation:

    • Try to schedule time outdoors for sports and other recreational activities before 10am and after 4pm. By doing this you will avoid excessive exposure to UVA and UVB radiation. The amount of UV radiation depends on the angle of the sun, not how hot or bright it appears outside. Clouds and haze do not block harmful radiation.
    • When outdoors, wear clothes that cover as much skin as possible; such as lightweight, long-sleeved shirts, long pants, and a broad-brimmed hat.
    • Use particular care around reflective surfaces such as water, sand, concrete, and white-painted areas.
    • Everyone over 6 months of age should use a broad-based sunscreen that protects from UVA and UVB rays, and has a skin protection factor (SPF) of at least 15. Use SPF 30 or higher if you burn easily, or are at high altitudes where sunlight is more intense. Apply to exposed skin and re-apply every two hours, or after exercising or going in the water. Use a higher SPF factor for more intense conditions, e.g., high altitudes, skiing, or the beach. Sunblocks, products that contain zinc or titanium oxide, and are even more effective than sunscreens, but are less popular because they tend to be pasty and white.
    • Parents should shield children under 6 months of age from intense sun exposure, and should protect them with clothing when sun exposure is unavoidable.
    • Never go to tanning parlors or use sun lamps. Even though they use mostly UVA rays and do not cause sunburn, they are still believed to be associated with skin cancer. Don't believe advertising claims that they are safe.

    Check your skin regularly and have your doctor do so as well at your annual checkup. Experts recommend that individuals conduct a thorough screening of their own skin periodically. Having a partner check your back and other hard-to-see places is ideal. Draw a map of your body and indicate the location of moles, areas of discoloration, and other blemishes. Each month note if a new growth has developed, or if there has been any change in shape, color, or size of lesions. See your doctor if you have any questions or suspicions.

    At your annual checkup, ask your provider to look at your skin, especially in areas you can't see. People with major risk factors, such as a history of significant sun exposure, multiple moles, and a fair complexion with a history of burning easily, should be checked at least annually by a dermatologist.

  • Prevention and Screening

    Protection from excessive sun exposure—especially though frequent use of sunscreen with SPF 15 or higher, protective clothing, and avoiding the midday sun—is essential for reducing the risk of all types of skin cancer. Light-skinned individuals who burn easily should be especially cautious. The following precautions should be taken by everyone to guard against excessive exposure to UVA and UVB radiation:

    • Try to schedule time outdoors for sports and other recreational activities before 10am and after 4pm. By doing this you will avoid excessive exposure to UVA and UVB radiation. The amount of UV radiation depends on the angle of the sun, not how hot or bright it appears outside. Clouds and haze do not block harmful radiation.
    • When outdoors, wear clothes that cover as much skin as possible; such as lightweight, long-sleeved shirts, long pants, and a broad-brimmed hat.
    • Use particular care around reflective surfaces such as water, sand, concrete, and white-painted areas.
    • Everyone over 6 months of age should use a broad-based sunscreen that protects from UVA and UVB rays, and has a skin protection factor (SPF) of at least 15. Use SPF 30 or higher if you burn easily, or are at high altitudes where sunlight is more intense. Apply to exposed skin and re-apply every two hours, or after exercising or going in the water. Use a higher SPF factor for more intense conditions, e.g., high altitudes, skiing, or the beach. Sunblocks, products that contain zinc or titanium oxide, and are even more effective than sunscreens, but are less popular because they tend to be pasty and white.
    • Parents should shield children under 6 months of age from intense sun exposure, and should protect them with clothing when sun exposure is unavoidable.
    • Never go to tanning parlors or use sun lamps. Even though they use mostly UVA rays and do not cause sunburn, they are still believed to be associated with skin cancer. Don't believe advertising claims that they are safe.

    Check your skin regularly and have your doctor do so as well at your annual checkup. Experts recommend that individuals conduct a thorough screening of their own skin periodically. Having a partner check your back and other hard-to-see places is ideal. Draw a map of your body and indicate the location of moles, areas of discoloration, and other blemishes. Each month note if a new growth has developed, or if there has been any change in shape, color, or size of lesions. See your doctor if you have any questions or suspicions.

    At your annual checkup, ask your provider to look at your skin, especially in areas you can't see. People with major risk factors, such as a history of significant sun exposure, multiple moles, and a fair complexion with a history of burning easily, should be checked at least annually by a dermatologist.

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