This small congenital nevus has a very low risk for malignant change.

CONGENITAL NEVUS, SMALL AND MEDIUM

The congenital melanocytic nevus (CMN) is a melanocytic lesion present at or soon after birth.

CMN may be small, medium or large (LCMN). For the LCMN, the subtypes giant and and bathing trunk nevi have been used.
The risk of melanoma in small and medium sized CMN is very low.
When two more CMN exist and there is any extracutaneous abnormality (e.g. facial feature, neurologic abnormalities on MRI), the term CMN syndrome is used.
The majority of patients with two or more CMN or the CMN syndrome have mosaicism for oncogenic mutations in codon 61 of NRAS (mosaic RASopathy).
It is recommended that any patient with 2 or more CMN should get a CNS MRI with contrast. An abnormal CNS MRK confers a higher risk for melanoma.

Classification

Type	Diameter (in an adult)	Frequency	Lifetime Risk of Melanoma
Small	< 1.5 cm	Common	< 1%
Medium	1.5-19.9 cm	Uncommon	< 1%
Large	>= 20 cm.	Rare	5-6%.
Giant	> 40 cm	Rare	5-6% or higher.

Diameter at birth that translates to 20 cm in adulthood

Location	Diameter
Head	12 cm
Hands, feet, torso, forearms, arms, and buttocks	7 cm
Thighs	5.8 cm
Legs	6 cm

Clinical

In the newborn, the congenital nevus is often flat, resembling a cafe au lait macule. Later, it usually thicken slightly and develops a mildly irregular, verrucous surface. Hypertrichosis with terminal hairs occurs in up to 75%. Commonly smaller, darker macules or papules may develop in the center of larger lesions. Sometimes, a pigmented lesion at birth is not diagnosable clinically. Biopsy may show such lesions to be melanocytic nevi, lentigines, cafe au lait macules, or non-specific fibrosis with increased capillaries.

Location

CMN may occur anywhere on the body, even rarely in the mouth. Hypoplasia of the underlying fat may occur. CMN of the scalp may be associated with cutis verticis gyrata.

Melanoma and Small or Medium MN

The risk of development of melanoma in the small and medium sized nevi is small--less than 1%. For example, one study of 227 medium-sized congenital nevi with an average follow up of 6.7 years did not find any developing melanoma.

Melanoma in LCMN

The lifetime risk of melanoma in patients with LCMN is probably 5% or less.

Neurocutaneous Melanosis

For large lesions over the scalp, the possibility of associated leptomeningeal melanocytosis should be considered. MRI is helpful in detecting this feature. Large melanocytic nevi over the spine may be associated with a tethered cord. MRI may be used here as well. Two or more congenital melanocytic nevi of any size are also associated with neurocutaneous melanosis and/or melanoma. It has been recommended that any child born with two melanocytic nevi should have an MRI to check for brain involvement within the first 6 months of life.

Melanoma developing in a congenital nevus. Although rare, it does happen.

Melanoma developing in a congenital nevus.

Medium-sized congenital nevus

Congenital Nevus with large Lipoma. Imaging of the spine should be done.

RegionalDerm

It is not the intention of RegionalDerm.com to provide specific medical advice, diagnosis or treatment. RegionalDerm.com only intends to provide users with information regarding various medical conditions for educational purposes and will not provide specific medical advice. Information on RegionalDerm.com is not intended as a substitute for seeking medical treatment and you should always seek the advice of a qualified healthcare provider for diagnosis and for answers to your individual questions. Information contained on RegionalDerm.com should never cause you to disregard professional medical advice or delay seeking treatment. If you live in the United States and believe you are having a medical emergency call 911 immediately.