Congenital melanocytic nevus

Congenital melanocytic nevus

Chris Schach

Author Bio -


Key Points
* Mole found at birth
* Occurs in 1% of infants
* Moles generally larger than acquired Moles
* Three types

A congenital melanocytic nevus, or birthmark, is a type of mole found in infants at birth. It’s usually larger in diameter than those that occur later in life, and may present an excess amount of hair. Some of these moles are removed for cosmetic reasons, and giant nevi are often excised to prevent cancer, as 5 to 15 percent of giant congenital melanocytic nevi may develop into melanoma.  Small and medium nevi have less than a 1% chance of developing into melanoma.

There are three types of Congenital Melanocytic Nevus.

*Giant congenital melanocytic nevus — Characterized by large size.  Greater than 20cm diameter and sometimes referred to as bathing trunk nevi due to size and distribution.  They darkly pigmented and sometimes hairy 
*Medium-sized congenital melanocytic nevus — characterized as having a diamater larges than 2 centimeters but smaller than 20 centimeters
*Small-sized congenital melanocytic nevus — characterized as having a diamater smaller than 2 centimeters

Differential Diagnosis (Other conditions with similar appearance)

Epidermal Nevus Syndrome
Nevus Sebaceus
Halo nevus
Malignant Melanoma
Seborrheic Keratosis

Congenital melanocytic nevus is generally apparent by sight at birth. The moles are flat and brown to black in color, and will grow proportional to body size. Sometimes biopsies are taken to see if the moles are benign or malignant.

* Most nevi may be left in place and monitored for change.  Giant congenital nevi are usually excised due to their increased risk of developing melanoma.

Evaluation by a dermatologist is recommended.  Surgical excision is the proper treatment for giant nevi but is not usually necessary for small and medium nevi.