Pigmented Skin Lesions, Types of Moles

The Melanoma Book
by Howard L. Kaufman, M.D., FACS

(Page 4 of 5)

Pigmented Skin Lesions

In addition to the non-pigmented skin lesions I've mentioned above, there is another broad category: pigmented skin lesions. They include both benign and malignant forms. Benign pigmented skin lesions, which comprise the majority, are called moles. Malignant pigmented skin lesions are called melanoma. Melanocytes, the cells that produce the pigment melanin, are the most common source of both kinds of pigmented skin growths. Melanoma occurs only when the melanocytes become severely abnormal and start dividing uncontrollably.

Moles are a normal part of the skin. When melanocytes, which are distributed in the lower layers of the epidermis throughout the body, grow in clusters with surrounding normal cells, a mole occurs. The difference between a mole and melanoma is that the melanocytes stop dividing in the mole but continue to grow without stopping in a melanoma. Moles can develop anywhere on the body that is covered by skin. The typical mole appears as a small flat or slightly raised growth of pink, tan, or brown coloration. Moles are usually symmetrical, which means the border is very smooth. Some moles may be unusual and can lead to cancer.

Everybody has moles between ten and forty is considered normal. Both children and adults may develop new moles (although the growth of new moles is less common after about forty years of age). Sometimes moles may grow and lift off the skin, but they are usually smaller than a pencil eraser. Moles may also fade or disappear completely over time.

The number and size of moles may be important factors in predicting the risk of melanoma. Interestingly, the number of moles is genetically determined, as demonstrated by the fact that identical twins have exactly the same number of moles, but non-identical twins do not. The risk of melanoma increases in people with more than fifty moles that are larger than two millimeters in diameter and in people with five or more moles larger than five millimeters in diameter.

Types of Moles

Doctors refer to a mole as a nevus, and multiple moles are called nevi. The common nevus is a typical mole and is sub-categorized by the pathologist depending on where the growth is located in the layers of the skin:

• a junctional nevus occurs only in cells in the epidermis
• a compound nevus contains cells in both the epidermis and dermis
• a dermal nevus is a mole in which cells are confined to the dermis. Dermal nevi may not appear pigmented since they are below the epidermis.

The blue nevus, a variant of the common nevus, is named for the blue color caused by the melanin-containing cells deep within the epidermis. Most common in women, it can occur in children and young adults. These nevi develop on the scalp, hands, and feet and are considered benign lesions. But treatment by simple surgical excision is usually recommended because, on rare occasions, melanoma can develop in a blue nevus.

A common nevus occasionally develops unusual features that distinguish it from all the others. These unusual moles are called atypical or dysplastic nevi, and differ from common nevi in several ways. First, atypical nevi are larger than five millimeters in diameter. In addition, these lesions may have inconsistent coloration, irregular or notched edges, and blurry borders. These lesions are sometimes smooth, but have also been described as scaly or 'pebbly.'

Atypical nevi are more likely than common nevi to develop into melanoma, although the exact relationship between atypical nevi and melanoma remains the subject of some speculation among experts. Any signs of a change in a mole, including an increase in the size of the mole, change in the edges, color, or new bleeding from the mole, all warrant evaluation by a medical professional. Atypical nevi are found in about 5 percent of the general population but in 30-40 percent of patients with melanoma, suggesting a strong correlation. There are many more patients with atypical nevi that do not develop melanoma, however, so other factors are likely involved as well.

A congenital nevus is an elevated, pigmented lesion present at birth in some babies. These lesions, which can vary in size and be quite large, have been suspected of increasing the risk of melanoma, a rare but possible occurrence in children. The risk seems to be related to the size of the congenital nevus, with those that cover more than 5 percent of the child's body, roughly equivalent to the right leg of an average two-year-old, having a significant risk. Since almost half the melanomas arising from congenital nevi occur in the first ten years of life, large congenital nevi should be removed as early as possible.

Another lesion that can be difficult to distinguish from melanoma in children is called a Spitz nevus (named after the pathologist who first reported it). These are usually small pinkish nodules, although they may also be pigmented. Spitz nevi are considered benign, but must be reviewed by an experienced pathologist to make certain.

Common Benign Pigmented Skin Lesions

• Common nevus
• Blue nevus
• Atypical or dysplastic nevus
• Congenital nevus
• Spitz nevus

Now that I've described the non-pigmented skin cancers and the benign pigmented skin lesions, only one category is left: malignant pigmented skin lesions, more commonly known as melanoma.

What Is Melanoma?

The appearance of melanoma is often obvious to professionals who treat the disease on a regular basis, but there are no absolute criteria that determine if a particular lesion is a melanoma. Melanomas are as diverse in appearance as people are, and therefore a challenge to identify through visual inspection alone. Any suspicious skin lesion should be considered for a biopsy, as this is the only way to know for certain if it is a melanoma. Some melanomas may start from a mole that has been present for many years, but increases in size, changes in its borders, or begins to bleed. Other melanomas may start as a new pigmented lesion that starts to grow in a normal area of the skin. Most melanomas are irregular in shape with uneven areas raised above the skin, although some may grow just below the skin and be felt as a hard nodule. Many melanomas are dark brown or even black in color, but some may be reddish or blue in color, and others may even be flesh colored. Some melanomas may develop areas of bleeding, a process referred to as ulceration.

I am suspicious, then, that it may be melanoma when I see a mole change in appearance or begin to bleed, or the development of a new pigmented skin lesion in a previously normal area of skin.

Please remember that most skin growths, or lesions, are not melanoma, and are not even cancerous. Furthermore, of all skin cancers, only about 5 percent are melanoma. That is precisely why determin- ing the source of skin cancers is so essential, since the non-melanoma cancers are more easily treated and the diagnosis of melanoma warrants more attention. Even though the odds favor a benign skin lesion, al- ways try to find out as soon as possible that a new growth or a change in a known mole definitely is not melanoma: Early recognition saves lives.

Copyright © 2005 Howard L. Kaufman, M.D., FACS

About the Author

Dr. Howard L. Kaufman is founder and Co-Director of the Columbia University Melanoma Center, attending physician at The New York Presbyterian-Columbia University Medical Center, chief of surgical oncology, and associate professor of surgery at Columbia University College of Physicians and Surgeons. He has conducted numerous clinical research trials on vaccines for cancer, lectures widely on cancer treatment and has published more than 100 articles in the field of tumor immunology and immunotherapy. He lives in New York City.