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Moles (Benign Pigmented Lesions, Benign Melanocytic Lesions, Melanocytic Naevi, Nevocytic Naevi)

Human Epidermis Skin Illustration

What is Moles (Benign Pigmented Lesions, Benign Melanocytic Lesions, Melanocytic Naevi, Nevocytic Naevi)?

Benign pigmented lesions refer to a wide range of abnormalities that can be found on the skin, including:

The ‘common mole‘ refers to a topic of significant importance. A very important life-threatening condition, malignant melanoma, can mimic these benign looking moles. With the naked eye, it may be difficult to tell benign from malignant lesions, thus awareness and presenting to your local health professional with any lesions of concern is recommended.

The term ‘mole‘ usually refers to a lesion which has a local excess of one or more normal constituents of the skin. Different groups of moles exist, depending upon their location in the skin. These moles are localized proliferations of pigment cells in the skin, called melanocytes. If they remain in contact with the dermal epidermal junction they are called junctional moles. If they become detached as a layer and lie free in the dermis, they are called intradermal moles. In the compound mole, both of these patterns are present simultaneously.

Statistics

Moles are extremely common in the general population, especially in fair skinned people. The prevalence in ethnic groups with dark skin is lower than that observed in individuals with fair skin. An individual in Australia may have at least 30-40 moles on their body.

Risk Factors

Studies show that the numbers of moles found in the Australian population decrease the further away you are from the equator. As the number of moles found on an individual is a major risk factor for melanoma, it is very important to adhere to guidelines for appropriate sun exposure and protection.

Most moles appear after birth, with approximately 1% present at birth. Childhood sun exposure is strongly associated with increased numbers of moles. There is also a genetic component suggested in some cases – the pattern of moles found on an individual is often similar for members of a family.

Progression

Benign pigmented moles made of melanocytes are defined as those lesions which do not produce any harmful effects. The main danger is related to the fact that these pigmented lesions can be found in association with melanoma. The true frequency of transformation of a pigmented lesion into melanoma is not known, and some studies show a low rate of change. Others have shown a higher rate, with up to a 40% change in some cases. Both acquired and congenital moles hold some risk for the development of melanoma.

Warning signs that a benign mole may be undergoing malignant transformation to a melanoma include: a rapid change in the mole, particularly in the size or if the mole becomes irregular around the borders. Itch and ulceration or bleeding are also danger signs. If any of these occur, you should seek urgent medical help immediately.

In a study conducted on 289 cases of melanoma, a pre-existing mole was associated with melanoma in 51% of cases. These results demonstrate that commonly acquired moles and dysplastic moles can be precursors of melanoma.

Symptoms

When you visit the doctor, he or she may ask questions, as necessary, to try and identify the most likely diagnosis and cause for your moles.

An important distinguishing feature is whether the mole has been there since birth or whether it has developed over the years. If it has developed over the years, the doctor may want to know how the mole has changed – symptoms such as pain, itching, bleeding, ulceration or any irriation are very important to report to your doctor. A change in size or the surface of the mole is also a significant event and should be immediately brought to you doctor’s attention.

A family history of melanoma or any dysplastic naevus syndromes should be reported to your doctor. If there is a positive family history, you may be required to remain under closer observation than usual, to detect any significant changes as soon as possible.

If there are any concerns about moles or other suspicious looking lesions that you find on your body, a prompt medical opinion is recommended.

Clinical Examination

The diagnosis of a benign mole is based predominantly upon what is visible to the eye, clinically. Some lesions that look similar to moles include: seborrheic keratoses, which are also benign lesions that have a warty, scaly, stuck on appearance. These are common in older age. Another important condition to rule out are melanomas – these are usually larger in size, exceeding 0.6 cm in diameter and characterized by irregular borders, asymmetry, and variable pigmentation.

When your doctor examines you, he or she may look for the following features on your skin. A full body skin check may be carried out, to make sure no moles are missed. Moles are commonly tan to brown in colour, but can be variable in colour, ranging from almost skin colour, to jet black. The exact dimensions, location and distribution of the moles are usually documented, so their progress can be monitored.

There are specific features unique to different types of benign moles. These include:

  • Congenital melanocytic naevi: These vary in size, from small (< 1 cm), intermediate (1-3 cm) to large (> 3 cm). Often the colour is evenly distributed throughout the mole.
  • Acquired melanocytic naevi: These are typically less than a centimeter in diameter and also evenly coloured. Junctional moles are usually flat, and brown to black in colour. Compound/intradermal moles are elevated, and tan to light brown in colour.
  • Spitz naevi: These moles tend to present as pink papules on the head of the child, but can exhibit variable colour and may be clinically indistinguishable from normal moles.
  • Blue naevi: These naevi have a lot of pigmentation within them, and because of the presence of deep pigmentation, the brownish black pigment present imparts a bluish cast to the mole, resulting in it’s name. They are usually quite small in size and symmetrical, often located on the distal arms or legs, or scalp and are firm and nodular.

How is it Diagnosed

There are no laboratory studies that are routinely performed if you have been diagnosed with common acquired or congenital moles. If there are any suspicious features about the lesion/s found on your body, the doctor may arrange for a simple excisional biopsy. This will allow both removal and accurate diagnosis of a mole. All removed moles are then sent for analysis under the microscope.

Prognosis

The chance of these benign moles undergoing a change, into a malignant lesion that we have to be worried about, depends greatly on the type and degree of change that the mole exhibits under the microscope. Many lesions have a very low risk of melanoma, whereas others (such as the large giant congenital pigmented hairy mole or bathing trunk mole) have a much higher risk of developing into melanoma. There is an atypical naevus syndrome, where patients may have more than 75 to 100 moles, a strong family history of melanoma, and an extremely high risk of developing melanoma. Regardless of the case, you should have your moles closely monitored by your local health professional.

Treatment

Most common moles do not require any medical or surgical treatment. They are benign by definition and medical treatment is typically ineffective and not warranted in management of a benign mole.

Moles can be surgically removed if you are troubled by their cosmetic appearance or they interfere functionally, with everyday life. If removing moles for cosmetic reasons, a tangential or shave excision is usually recommended. Larger lesions (exceeding 1 cm in diameter) may require complete excision with closure with stitches.

If there is any doubt about a mole’s potential for malignant transformation into a melanoma, complete excision of the mole with narrow margins is recommended. The specimen is then sent for examination under a microscope and an accurate diagnosis can be made.

References

  1. Skender-Kalnenas D, Dallas R, Heenan J. Benign melanocytic lesions: Risk markers or precursors of cutaneous melanoma? J Am Acad Dermatol. 1995;33(6):1000-7. [Abstract]
  2. Buxton P. ABC of Dermatology. London: BMJ Publishing; 2005. [Book]
  3. McCalmont T. Melanocytic nevi [online]. Omaha, NE: eMedicine; 2006 [cited 19 December 2006]. Available from: URL link
  4. Harrison S, Buettner P, MacLennan R. Body-site distribution of melanocytic nevi in young Australian children. Arch Dermatol. 1999;135(1):47-52. [Abstract | Full text]
  5. Kopf A, Bart R, Hennessey P. Congenital nevocytic nevi and malignant melanomas. J Am Acad Dermatol. 1979;1(2):123-30. [Abstract]
  6. Marghoob A, Schoenbach S, Kopf A, et al. Large congenital melanocytic nevi and the risk for the development of malignant melanoma: A prospective study. Arch Dermatol. 1996;132(2):170-5. [Abstract]
  7. Zalaudek I, Hofmann-Wellenhof R, Cerroni L, Kerl H. White dysplastic melanocytic naevi. Lancet. 2002;359(9322):1999-2000. [Abstract]
  8. Cotran RS, Kumar V, Collins T, Robbins SL. Robbins Pathologic Basis of Disease (6th edition). Philadelphia, PA: WB Saunders Company; 1999. [Book]
  9. Naeyaert J, Brochez L. Clinical practice: Dysplastic nevi. N Engl J Med. 2003;349(23):2233-40. [Abstract]
  10. Rotstein H, De Launey WE, Land WA. Principles and Practice of Dermatology. Sydney, NSW: Butterworth-Heinemann; 1998. [Book]

Dates

Posted On: 20 December, 2006
Modified On: 19 March, 2014

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