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Melanocytic nevus



Melanocytic nevus
Classification & external resources
Mole, more specifically an intradermal nevus
ICD-10 D22.
ICD-9 216
DiseasesDB 8333
eMedicine derm/289 
MeSH D009508

A mole, technically known as a melanocytic naevus, is a small, dark spot on human skin. According to the American Academy of Dermatology, the majority of moles appear during the first two decades of a person’s life while about one in every 100 babies are born with moles[citation needed]. Acquired moles are a form of benign neoplasm, while congenital moles are considered a minor malformation, or hamartoma. A mole can be either subdermal (composed of melanin), or a pigmented growth on the skin, formed mostly of a type of cell known as melanocytes. The high concentration of the body’s pigmenting agent, melanin, is responsible for their dark color. Moles are a member of the family of skin lesions known as naevi.

Contents

Classification

Melanocytic nevi represent a family of lesions. The most common variants are :

  • Junctional nevus: the nevus cells are located along the junction of the epithelium and the underlying dermis. A junctional nevus is flat and brown to black.
  • Compound nevus: a mixture of junctional and intradermal proliferation. Compound nevi are slightly raised and brown to black. Beauty marks are usually compound nevi.
  • Intradermal nevus: the nevus cells are located in the dermis only. Intradermal nevi are raised; most are flesh-colored (not pigmented).
  • Dysplastic nevus (nevus of Clark): usually a compound nevus with cellular and architectural dysplasia. They tend to be larger (more than 6 mm), with irregular borders and irregular coloration. Hence, they ressemble melanoma, appear worrisome and are often removed to clarify the diagnosis. Dysplastic nevi do not transform into melanoma but are a marker of risk when they are numerous (atypical mole syndrome).
  • Blue nevus: the nevus cells are very deep in the dermis.
  • Spitz nevus: a distinct variant of intradermal nevus, usually in a child. They are raised and reddish (non-pigmented). A pigmented variant, called the nevus of Reed, typically appears on the leg of young women.
  • Giant Hairy Nevus: these large, pigmented, often hairy congenital nevi can be a source of much psychological and social suffering. They are also important because melanoma may occasionally (10 to 15%) appear in them.
  • Intramucosal nevus: junctional nevus of the mucosa of the mouth or genital areas. In the mouth, they are found most frequently on the hard palate.
  • Nevus of Ito and Nevus of Ota: congenital, flat brownish lesions on the face or shoulder.
  • Mongolian spot: congenital large, deep, bluish discoloration on the back of Asian babies.

History

At one time in the 1950s and 60s, (and, to lesser extent, currently) a mole was known as a "beauty mark" when it appeared in certain spots on a woman’s face. Examples include Marilyn Monroe, model Cindy Crawford and singer Madonna. Madonna's facial mole -- below her right nostril -- has been surgically removed.[citation needed] Almost everyone with light skin has at least one or two moles somewhere on their bodies while large numbers can be concentrated on the back, chest, and arms. Darker skin shades, however, tend to have fewer moles. Some folklore about moles includes the notion that picking at a mole can cause it to become cancerous or grow back larger. While chronic picking or irritation (by clothing) of a mole can be detrimental in many ways, it has not been associated with a higher incidence of cancer.[1] But while a mole may sometimes be removed by its bearer and may not grow back larger, the resulting scar can be larger. When a mole is bothersome, physicians usually recommend that it be examined by a dermatologist to see if it should be removed. The dermatologist or plastic surgeon can perform the procedure with an eye toward preventing a larger scar.

Cause and prevention

Genes

Genes can have an influence on a person's moles.

Dysplastic nevi and atypical mole syndrome is a hereditary condition which causes the person to have a large quantity of moles (often 100 or more) with some larger than normal or atypical. This often leads to a higher risk of melanoma, a serious skin cancer.[2] In the overall population, a slight majority of melanomas do not form in an existing mole, but rather create a new growth on the skin. Nevertheless, those with dysplastic nevi are at a higher risk of melanoma occurring not only where there is an existing mole, but surprisingly, also where there are none.[3][4] Such persons need to be checked regularly for any changes in their moles and to note any new ones.

Sunlight

Some scientists suspect that overexposure to ultraviolet light, including excessive sunlight, may play a role in the formation of acquired moles.[5] However, more research is needed to determine the complicated relationship between one's heredity and overall exposure to ultraviolet light. A strong indication that this is so (but falling short of proof), is the relative lack of moles on the buttocks of people with dysplastic nevi.

Because studies have found that sunburns and too much time in the sun can increase the risk factors for melanoma, the American Academy of Dermatology recommends staying out of the sun between 10 a.m. and 3 p.m. standard time (or whenever your shadow is shorter than your height), forgoing tanning booths, and wearing sun block, a hat and sunglasses outdoors.

Appearance

According to the American Academy of Dermatology, the most common types of moles are skin tags, raised moles and flat moles. Untroublesome moles are usually circular or oval and not very large. Some moles typically produce dark, coarse hair that can be cause for social rejection. Common mole hair removal procedures include plucking, cosmetic waxing, electrolysis, SUPER electrolysis, threading, cauterization, and very careful nuclear bombardment.

Differentiation from melanoma

It often requires a dermatologist to fully evaluate moles. For instance, a small blue or bluish black spot, often called a blue nevus, is usually benign but often mistaken for melanoma.[6] Conversely, a junctional nevus, which develops at the junction of the dermis and epidermis, is potentially cancerous.[7]

A basic reference chart used for consumers to spot suspicious moles is found in the mnemonic, A-B-C-D. The letters stand for Asymmetry, Border, Color and Diameter. Sometimes, the letter E (for Evolving) is added. According to the American Academy of Dermatology, if a mole starts changing in size, color, shape or, especially, if the border of a mole develops ragged edges or becomes larger than a pencil eraser, it would be an appropriate time to consult with a physician. Other warning signs include a mole, even if smaller than a pencil eraser, that is different than the others and begins to crust over, bleed, itch, or becomes inflamed. The changes may indicate developing melanomas. The matter can become clinically complicated because mole removal depends on which types of cancer, if any, comes into suspicion.

Complications

Experts say that vast majority of moles are benign. Nonetheless, the National (U.S.) Cancer Institute reported 59,940 new cases of melanoma by June, 2007, with 8,110 deaths.[8]

Mole removal

If a mole is highly suspicious of being a melanoma, then it might need to be removed and biopsied (microscopic evaluation by a pathologist). Other reasons for removal may be cosmetic, or because a raised mole interferes with daily living (e.g. shaving). They leave a red mark on the site which morphs back to the patient’s usual skin color in about two weeks. However, there might still be a risk of spread of the melanoma, so the methods of Melanoma diagnosis, including e.g. excisional biopsy. Moles can be removed by laser, surgery or electrocautery.

In properly trained hands, some medical lasers are used to remove flat moles level with the surface of the skin, as well as some raised moles. While laser treatment is commonly offered and may require several appointments, other dermatologists think lasers are not the best method for removing moles because the laser only cauterizes or, in certain cases, removes very superficial levels of skin. Moles tend to go deeper into the skin than non-invasive lasers can penetrate. After a laser treatment a scab is formed, which falls off about seven days later, in contrast to surgery, where the fissure has to be stitched with sutures.

For surgery, many dermatologic and plastic surgeons first use a freezing solution, usually liquid nitrogen, on a raised mole and then shave it away with a scalpel. If the surgeon opts for the shaving method, he or she usually also cauterizes the stump. Because a circle is difficult to close with stitches, the incision is usually elliptical or eye-shaped.

Electrocautery is also used for removing skin tags and only reaches the outermost level of skin so that scarring is not a problem.

See also

References

  1. ^ P. Kaskel, P. Kind, S. Sander, R.U. Peter, G. Krahn (2000) Trauma and melanoma formation: a true association? British Journal of Dermatology 143 (4), 749-753
  2. ^ Burkhart, C.G MPH, MD. Dysplastic nevus declassified; even the NIH recommends elimination of confusing terminology. SKINmed: Dermatology for the Clinician 2(1):12-13, 2003.
  3. ^ D.J. Pope, T. Sorahan, J.R. Marsden, P.M. Ball, R.P. Grimley and I.M. Peck. Benign pigmented nevi in children. Arch of Dermatology 2006;142:1599-1604
  4. ^ D.E. Goldgar, L.A. Cannon-Albright, L.J. Meyer, M.W. Pipekorn, J.J. Zone, M.H. Skolnick. Inheritance of Nevus Number and Size in Melanoma and Dysplastic Nevus Syndrome Kindreds. Journal of the National Cancer Institute 1991 83(23):1726-1733
  5. ^ Arne van Schanke, Gemma M.C.A.L. van Venrooij, Marjan J. Jongsma, H. Alexander Banus, Leon H.F. Mullenders, Henk J. van Kranen and Frank R. de Gruijl. Induction of Nevi and Skin Tumors in Ink4a/ArfXpa Knockout Mice by Neonatial, Intermittent, or Chronic UVB Exposures. Cancer Res 2006; 66 (5), 2608-15.
  6. ^ Granter, Scott R. M.D.; McKee, Phillip H. M.D., F.R.C. Path.; Calonje, Eduardo, M.D.; Mihm, Martin C. Jr., M.D.; Busam, Klaus, M.D. Melanoma Associated with Blue Nevus and Melanoma Mimicking Cellular Blue Nevus: A Clinicopathologic Study of 10 Cases on the Spectrum of So-called ‘Malignant Blue Nevus’. American Journal of Pathology. 25(3):316-323, March 2001.
  7. ^ Hall J., Perry, VE Tinea nigrra palmaris: differentiation from malignant melanoma or juncional nevi. Cutis. 1998 Jul;62(1):45-6
  8. ^ http://www.nci.nih.gov/cancertopics/types/melanoma
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Melanocytic_nevus". A list of authors is available in Wikipedia.
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