SkinCancerNet Article
Four Types of Melanoma

Melanoma, also referred to as “malignant melanoma,” is the most serious form of skin cancer because - with the exception of some rare forms of skin cancer - it is the skin cancer most likely to spread to lymph nodes and internal organs. Today, melanoma accounts for 77% of all deaths from skin cancer.

Dermatologists believe that the number of deaths from melanoma could be significantly reduced if more people were able to recognize melanoma in its earliest stages. It is important to know that there are different types of melanoma. This article describes the four most common types of melanoma, which accounts for about 100% of diagnosed cases. Below you will find an explanation of what each of these four types of melanoma looks like and important points to remember. Here are a few of these key points:

• With early detection and treatment, the cure rate for melanoma is about 95%.

• Not all melanoma develops from a changing mole. Melanoma also can appear where there was not a previous lesion and look like a non-pigmented scar or cyst.

• Melanoma can appear as a nail streak or non-healing bruise.

Four Types of Melanoma

1. Superficial spreading melanoma (about 70% of diagnosed cases)

2. Nodular melanoma (about 15% of diagnosed cases)

3. Lentigo maligna melanoma (about 10% of diagnosed cases)

4. Acral lentiginous melanoma (about 5% of diagnosed cases)

Superficial Spreading Melanoma
Superficial spreading melanoma (SSM) is the most common type of melanoma in the United States, accounting for about 70% of all diagnosed melanoma cases. This type of melanoma can strike at any age and occurs slightly more often in females than males. SSM is the leading cause of death from cancer in young adults.

When SSM occurs in females, it most commonly appears on the legs. In males, it is more likely to develop between the neck and pelvis. However, this does not mean that females do not get SSM on their trunks or that males do not see SSM on their legs. This melanoma can occur anywhere on the skin’s surface.

What it looks like: A typical SSM lesion has:

• Irregular borders

• Various shades of black, brown, gray, blue, pink, red, or white. Within the lesion there can be a remarkable variation in color involving white, pink, brown, and black.

In the early stages, SSM usually appears as a flat spot that looks like a freckle that is spreading sideways on the skin. Over time, the pigmentation in the lesion may darken, and the lesion may grow, develop increasingly irregular borders, and have areas of inflammation within the lesion. The area around the lesion may begin to itch. Occasionally, a SSM may become “less” pigmented as a person’s immune responses try to destroy it. If a lesion becomes less pigmented, this does not mean that the lesion no longer requires treatment. It definitely needs to be examined by a dermatologist.

Superficial spreading melanoma (SSM) is the leading cause of death from
cancer in young adults

(Photos used with permission of the American Academy of Dermatology
National Library of Teaching Slides)

What to remember: Superficial spreading melanoma can progress rapidly. If you see a lesion that you suspect could be melanoma, have it examined by a dermatologist.

Nodular Melanoma
Nodular melanoma (NM) is the most aggressive type of melanoma and accounts for about 15% of all melanomas diagnosed in the United States. It can appear anywhere on the body and occurs more often in males than females. It can develop at any age; however, it is most often seen in people aged 60 and older.

NM differs from other types of melanoma in three ways:

• Tends to grow more rapidly in thickness (penetrate the skin) than in diameter

• May not have a readily visible phase of development

• Instead of arising from a pre-existing mole, it may appear in a spot where a lesion did not previously exist

Since NM tends to grow deeper more quickly than it does wide and can occur in a spot that did not have a previous lesion, the prognosis is often worse because it takes longer for a person to be aware of the changes.

What it looks like: NM is most often darkly pigmented; however, some NM lesions can be light brown or even colorless (non-pigmented). A light-colored or non-pigmented NM lesion may escape detection because the appearance is not alarming. An ulcerated and bleeding lesion is common.

The following photos show diagnosed cases of NM, which often appears as a dome-shaped, darkly pigmented lesion.

Nodular melanoma can appear anywhere on the body and develop in an area
that did not have a previous lesion.

(Photos used with permission of the American Academy of Dermatology
National Library of Dermatologic Teaching Slides)

What to remember: If a lesion appears where none existed before, have it examined as soon as possible by a dermatologist.

Lentigo Maligna Melanoma
Lentigo maligna melanoma (LMM) typically occurs on sun-damaged skin in the middle-aged and elderly, especially on the face. This melanoma may be mistaken in its early, and most treatable, stages for a benign "age spot" or "sun spot.” LMM accounts for about 10% of the melanomas diagnosed in the United States. Since LMM is so easily mistaken, it can go undetected for years. This can be quite dangerous.

What it looks like: LMM begins as a spreading, flat, patch with irregular borders and variable colors of brown. This lesion is called “lentigo maligna.” This spreading brownish patch may grow slowly for years and is often mistaken for lentigo simplex — a benign (non cancerous) brownish patch that can develop in the elderly after years of sun exposure.

As the lesion grows and evolves, both the pigmentation and borders tend to become more irregular. This often occurs slowly over a period of 10 to 15 years. It also can happen rapidly — in a matter of weeks or months. As the lesion grows deeper into the skin (thickness increases), it may become various shades of black and brown. Dark nodules may appear within the irregular borders. These nodules are the invasive tumor, and if large enough to be felt by touch, will feel lumpy.

What to remember: If you have a large pigmented patch of skin, especially one with an irregular border, see a dermatologist as soon as possible.

Acral Lentiginous Melanoma
In the United States, acral lentiginous melanoma (ALM) accounts for about 5% of all diagnosed melanomas. It also is the most common form of melanoma in Asians and people with dark skin, accounting for 50% of melanomas that occur in people with these skin types.

ALM is sometimes referred to as a “hidden melanoma” because these lesions occur on parts of the body not easily examined or not thought necessary to examine. ALM develops on the palms, soles, mucous membranes (such as those that line the mouth, nose, and female genitals), and underneath or near fingernails and toenails.

What it looks like: ALM is often overlooked until it is well advanced because in the early stages, it often looks like a bruise or nail streak. Here is what it usually looks like on each area of the body:

• Palm or sole – Melanoma usually begins as an irregularly shaped tan, brown, or black spot. It is often mistakenly attributed to some recent injury — that is, the patient recalls a relatively recent bruise or blow in the general area of the pigmented spot.

• Mucous membranes – When melanoma develops on a mucus membrane, it is most likely to develop inside the nose or mouth. Early symptoms include nosebleeds and nasal stuffiness and a pigmented mass inside the mouth. Melanomas also can develop on the mucous membranes of the anus, urinary tract, and female genitalia.

• Under a nail - The first sign may be a "nail streak" — a narrow, dark stripe under the nail. ALM usually develops on the thumb or big toe; however, it can occur under any fingernail or toenail. Many individuals, 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, a wide or very darkly pigmented streak, or a nail that is separating or lifting up from the nail bed should be examined by a dermatologist. A possible indication of advanced ALM is a nail streak with associated pigmentation in the nail fold skin or destruction of the nail plate.
  
  ALM of the fingers or toes also can develop without an obvious nail streak — particularly the non-pigmented variety. ALM may, for example, look very much like a chronic infection of the nail bed.

As an ALM tumor increases in size, it usually becomes more irregular in shape and color. However, some ALM lesions can be lightly colored or colorless. The surface of the ALM lesion may remain flat, even as the tumor invades deeply into the skin. Thickening ALM on the sole of the foot can make walking painful and be mistaken for a plantar wart.

These photos show different cases of acral lentiginous melanoma on the foot.
In its early stages, ALM is often mistaken for a bruise.

(Photos used with permission of the American Academy of Dermatology
National Library of Dermatologic Teaching Slides)

The second photo shown above depicts an advanced tumor. This patient believed he had a long-standing bruise on his toe and refused to be examined by a physician. By the time ALM was finally diagnosed and surgically removed, it had invaded deeply into tissue and spread to other organs. The patient died of metastatic melanoma.

What to remember: Be sure to see a dermatologist as soon as possible if you notice a:

• Bruise that does not fade or comes and goes

• Nail lifts up or separates from the nail bed

• New nail streak not associated with recent trauma

• Enlarging nail streak

• Wide or very darkly pigmented nail streak

• Pigmented mass in the mouth

• Nosebleeds and nasal stuffiness

Non-pigmented Subtypes
While uncommon, melanoma occasionally does not have brown or black pigmentation. An uncommon subtype called amelanotic melanoma usually appears as a pink or red nodule (lump). Another uncommon subtype, desmoplastic neutrotrophic melanoma (DNM), usually looks like a non-pigmented scar. When a scar or keloid appears on the skin and the skin has not been injured, DNM is suspected. The lesion also can appear as a cyst that may or may not be pigmented. DNM tends to appear on sun-damaged skin in elderly patients, occurring mostly on the head and neck.

All content solely developed by the American Academy of Dermatology