Welcome to this update of MelanomaNet, a patient education service of the American Academy of Dermatology supported by an unrestricted educational grant from Chiron Therapeutics and Chiron Corporation.

A melanoma is usually described as one of four types:

• superficial spreading melanoma—the most common type overall
• nodular melanoma—tends to increase in thickness more rapidly than in diameter
• lentigo maligna melanoma—melanoma developing in a "sun-induced" freckle
• acral lentiginous melanoma—melanoma appearing on palms of hands, soles of feet, nailbeds, and mucous membranes; relatively rare in white-skinned people, but accounts for about half of melanomas in non-whites.

In this update of MelanomaNet we describe each type and illustrate the descriptions with photos of typical appearances of each type. These descriptions and illustrations may (1) help you recognize suspicious lesions that should be examined by a dermatologist, or (2) if you have melanoma, help you better understand your disease.

MelanomaNet has a Glossary that defines and explains important terms. Words defined in the Glossary are bolded and linked in the text. Click on a bolded word to access the definition in the Glossary.

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• Superficial spreading melanoma (SSM) is the most common type of melanoma in the United States, accounting for about 70% of all melanoma cases in the U.S. SSM occurs slightly more often in females than in males. It is the leading cause of cancer deaths in young adults. In males the most frequent location of SSM is the body between the neck and the pelvis; in females, SSM occurs most frequently on the legs.

Here are three photos of typical SSM:

The typical appearance of SSM is a lesion with irregular borders, colored in various shades of black, brown, gray, blue, pink, red or white. Changes occurring in the lesion over time may include darker pigmentation, increase in size, more irregular borders, areas of inflammation within the lesion, and itchiness in or around the lesion. Occasionally a SSM may become less pigmented as it is destroyed by a person’s immune responses.

Because SSM may rapidly progress to become more malignant, a suspicious-looking lesion should be examined by a physician as soon as possible. For tips on how to examine yourself, and recognize a lesion that may be a melanoma, review the A-B-C-D examination.

• Nodular melanoma (NM). The growth of NM is vertical (thickness), deeper into tissues. NM is the most aggressive type of melanoma. As it grows into the tissues, the diameter may increase as well—the tumor becoming thicker and wider. This aggressive tumor may not have a readily visible superficial phase of development.

NM is different from other types of melanoma in another way: instead of arising from a pre-existing mole (nevus), it may arise spontaneously in a spot where no lesion existed before. NM can occur on any part of the body.

NM accounts for 15-25% of all melanomas in the U.S. It occurs more often in males than in females. While NM can occur at any age, it most often occurs in people aged 60 or more years.

The next three photos show typical appearances of NM—a dome-shaped, darkly pigmented lesion:

Although NM is most often darkly pigmented, some NM lesions can be light brown or even colorless (nonpigmented). A light-colored or nonpigmented NM lesion may escape detection because the appearance is not alarming. A good rule to remember is: if a lesion appears where none existed before, have it examined as soon as possible by your physician.

• Lentigo maligna melanoma (LMM) accounts for 8% to 12% of melanomas in the United States. LMM can be a dangerous melanoma because it may be ignored by the patient and by his/her family for years. LMM typically occurs on sun-damaged skin in older people, and may be mistaken in its early stages for a benign "age spot" or "sun spot" in its very early stages. LMM is usually preceded by lentigo maligna (LM), a pre-malignant lesion. Lentigo maligna (LM) appears as a flat "freckle" on sun-damaged skin.

A well-advanced LMM on the face of an elderly woman is shown in this photo:

A typical pre-malignant LM may be variegated brown in color with irregular borders. Both pigmentation and borders may become more irregular as the lesion enlarges and evolves into LMM—often slowly over a period of 10-15 years, or rapidly over weeks or months. As lentigo maligna (LM) progresses to lentigo maligna melanoma (LMM), the lesion may become variably black-and-brown in color. (Review A-B-C-D tips for self-examination in MelanomaNet Edition #1, and the importance of recognizing irregularities of color and shape of a pigmented lesion).

Progression of pre-cancerous LM to LMM represents the vertical (thickness) growth phase of the tumor. As LMM progresses, dark nodules may appear within the irregular borders of the lesion. These are nodules of invasive tumor which can be felt as "lumpiness" if they are large enough to be identified by touch.

• Acral lentiginous melanoma (ALM) is statistically relatively rare in the U.S. because it comprises about 5% of melanomas in the majority white-skinned population. Among dark-skinned and black people, however, ALM accounts for more than 50% of all melanoma cases in the U.S.

The incidence rate of ALM actually occurs with about equal frequency in people of all racial backgrounds. But, because the overall incidence of melanoma is much less in black people and Asians than in whites, ALM is the most common type of melanoma seen in black people and Asians in the U.S. It is important to note, however, that ALM can occur in anyone regardless of ethnic background. ALM has a peculiar pattern of occurrence: it occurs only on the palms of the hands, the soles of the feet, under or near fingernails and toenails, the mouth, and mucous membranes of anus and genitalia.

Only half of the melanomas occurring in non-whites is of the ALM type. Any other type of melanoma may occur in non-whites, but the likelihood is very low.

Here is a photo illustrating ALM of the foot:

The next photo illustrates ALM on toes:

(Photo used with permission of the American Academy of Dermatology
 National Library of Dermatologic Teaching Slides and the Sulzberger Institute for Dermatologic Education)

Because ALM of the plantar foot, toes or nailbeds is covered much of the day by footwear, it can be overlooked until it is far advanced. On either hands or feet, ALM may be overlooked because the lesion is considered to be a bruise. On the foot, ALM may be mistaken for a plantar wart. The next photo shows ALM on the toe of a middle-aged man who complained of a long-standing "bruise" on his toe, but refused to have it examined by a physician. When ALM was finally diagnosed and surgically removed, it had invaded deeply into tissue and spread to other organs. The patient died of metastatic melanoma.

(Photo used with permission of the American Academy of Dermatology
 National Library of Dermatologic Teaching Slides and the Sulzberger Institute for Dermatologic Education)

ALM of the palm of the hand or sole of the foot usually begins as an irregularly shaped tan, brown or black spot. It is frequently (and wrongly) attributed to some recent trauma—that is, the patient recalls a relatively recent bruise or blow in the general area of the pigmented spot. As the tumor increases in size, it usually becomes more irregular in shape and color, although some ALM lesions may be lightly colored or colorless. The surface of the ALM lesion may remain flat, even as the tumor invades deeply into the skin (thickness). Thickening ALM on the sole of the foot may become painful to walk on, and may be mistaken for a plantar wart.

ALM of the nail is most common on the thumb or big toe, but may arise in any fingernail or toenail. When ALM develops under the nail, the first sign may be a "nail streak"—a narrow, dark stripe under the nail. Many people—especially dark-skinned people—have fixed nail streaks that are completely benign. A new nail streak not associated with recent trauma, an enlarging nail streak, or a wide or very darkly pigmented streak should be examined by a dermatologist.

The possibility of an advanced ALM is also indicated by a nail streak and associated pigmentation in the nail fold skin, or destruction of the nail plate.

ALM of the fingers or toes can also develop without an obvious nail streak—particularly the nonpigmented variety. It may, for example, look very much like a chronic infection of the nail bed.

This review of the four types of melanoma is offered to help people recognize melanoma, and to better understand the disease.

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