Congenital melanocytic nevus

Congenital melanocytic nevus
Classification and external resources
Congenital nevus
ICD-10	D22 (ILDS D22.L60)

The congenital melanocytic nevus is a type of melanocytic nevus (or mole) found in infants at birth. This type of birthmark occurs in about 1% of infants in the United States; it is located in the area of the head and neck 15% of the time.

The congenital melanocytic nevus (plural, nevi) presents as a circumscribed, light brown to black patch or plaque, potentially very heterogeneous in consistency, covering any size surface area and any part of the body. The appearance of the congenital melanocytic nevus is similar to those of nevi acquired after birth. However, congenital ones are usually larger in diameter and may have excess terminal hair, a condition called hypertrichosis. If over 40 cm projected adult diameter with hypertrichosis, it is sometimes called giant hairy nevus; more usually these largest forms are known as large or giant congenital melanocytic nevus. The estimated prevalence for the largest forms is 0.002% of births^[1] .

Microscopically, congenital melanocytic nevi appear similar to acquired nevi with two notable exceptions. For the congenital nevus, the neval cells are found deeper into the dermis. Also, the deeper nevus cells can be found along with neurovascular bundles, with both surrounding hair follicles, sebaceous glands, and subcutaneous fat. Such annexes and the hypodermis can also be hypoplasic or, conversely, present aspects of hamartoma.

Many are surgically removed for aesthetics and relief of psychosocial burden, but larger ones are also excised for prevention of cancer, although the benefit is impossible to assess for any individual patient. Proliferative nodules are usually biopsied and are regularly but not systematically found to be benign^[2] . Estimates of transformation into melanoma vary from 2-42% in the literature, but are most commonly considered to be at the low end of that spectrum due to early observer bias^[3].

Types

Congenital melanocytic nevi may be divided into the following types:^[4]:690-1

• Large or giant congenital melanocytic nevus (Bathing trunk nevus, Giant pigmented nevus)
• Medium-sized congenital nevus
• Small-sized congenital nevus

Clinical Findings

The lesions are often flat at birth, brown to black in color . They often grow proportionally to the body size as the child matures. As they mature, they often develop thickness, and becomes elevated, although these features can also be present from birth. Prominent terminal hairs often form, especially after puberty. With maturity, the nevus can have variation in color, and the surface might be textured with proliferative growths.

Benign congenital nevi can have histological characteristics resembling melanomas, often breaking most if not all of the ABCD rules. Dermatoscopic findings of the smaller forms of benign congenital nevi can aid in their differentiation from other pigmented neoplasms^[5].

Malignancy Potential

Large and especially giant congenital nevi are at higher risk for malignancy degeneration into melanoma. Because of the premalignant potential, it is an acceptable clinical practice to remove congenital nevi electively in all patients and relieve the nevocytic overload.

Treatment

Surgical excision is the standard of care. Some individuals advocate the use of hair removal laser for the treatment of congenital nevi. While this is likely safe and effective for small congenital nevus, laser removal for larger lesions might pose a liability for the laser surgeon if malignancy developed from a deep (dermal) component of the nevus that is not reached by the laser. Repigmentation after laser treatment of congenital nevi or superficial curettage supports this concern.

See also

• List of cutaneous conditions

Notes

• Kahn, Michael A. Basic Oral and Maxillofacial Pathology. Volume 1. 2001.

References

1. ^ Price, HN; Schaffer, JV (2010 May-Jun). "Congenital melanocytic nevi-when to worry and how to treat: Facts and controversies.". Clinics in dermatology 28 (3): 293–302. PMID 20541682. 
2. ^ Phadke, PA; Rakheja, D, Le, LP, Selim, MA, Kapur, P, Davis, A, Mihm MC, Jr, Hoang, MP (2011 May). "Proliferative nodules arising within congenital melanocytic nevi: a histologic, immunohistochemical, and molecular analyses of 43 cases.". The American journal of surgical pathology 35 (5): 656–69. PMID 21436676. 
3. ^ Etchevers, Heather. "Large congenital melanocytic nevus". Orphanet: The portal for rare diseases and orphan drugs. Institut national de la santé et de la recherche médicale. http://www.orpha.net/consor/cgi-bin/Disease_Search.php?lng=EN&data_id=370&Disease_Disease_Search_diseaseGroup=626&Disease_Disease_Search_diseaseType=ORPHA&Disease%28s%29/group%20of%20diseases=Congenital-pigmented-nevus&title=Congenital-pigmented-nevus&search=Disease_Search_Simple. Retrieved 2 August 2011. 
4. ^ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0. 
5. ^ Brooks, Christine; Scope, Alon, Braun, Ralph P, Marghoob, Ashfaq A (February 2011). "Dermoscopy of nevi and melanoma in childhood". Expert Review of Dermatology 6 (1): 19–34. doi:10.1586/edm.10.71. http://www.expert-reviews.com/doi/full/10.1586/edm.10.71. 

External links

• Congenital Nevus photo library at Dermnet
• Nevus Outreach, Inc. -- http://www.nevus.org