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Giant pigmented nevus

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Giant pigmented nevus

Congenital melanocytic nevus
Classification and external resources
10 ICD-O: 8761/0

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

Classification

Congenital melanocytic nevi may be divided into the following types:[1]:690–1

  • Small-sized congenital nevocytic nevus is defined as having a diameter less than 2cm. [1]:690
  • Medium-sized congenital nevocytic nevus is defined as having a diameter more than 2cm but less than 20cm. [1]:690
  • Giant congenital melanocytic nevus (also known as "Bathing trunk nevus," "Garment nevus," "Giant hairy nevus", and "Nevus pigmentosus et pilosus") is defined by one or more large, darkly pigmented and sometimes hairy patches. [2] [1]:690

Signs and symptoms


The congenital melanocytic nevus appears 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.

As compared with a congenital melanocytic nevus, congenital melanocytic nevi 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.[3]

Melanocytic Nevi often grow proportionally to the body size as the child matures. As they mature, they often develop thickness, and become 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.

Diagnosis


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.[4]

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.

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.

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.[5] 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.[6]

Prognosis

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.

See also

Notes

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

References

External links

  • Congenital Nevus photo library at Dermnet
  • World-wide patient federation NaevusGlobal
  • Nevus Outreach, Inc. (USA) for English-language information on large or giant congenital melanocytic nevus
  • Caring Matters Now (U.K.) for English-language information on large or giant congenital melanocytic nevus
fr:Naevus
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