Congenital Nevi Workup

Updated: Apr 05, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Laboratory Studies

Biopsy confirms a benign or malignant nature in suggestive lesions.


Imaging Studies

In cases associated with a high index of suspicion for the presence of neurocutaneous melanosis, magnetic resonance imaging of the central nervous system is a useful diagnostic tool. The presence of a large congenital melanocytic nevus in an infant should prompt magnetic resonance imaging testing before age 4 months if it is in a posterior midline location or is associated with multiple satellite nevi. [24]

Congenital melanocytic nevi rarely involve underlying bones and the maxillary sinus. Such a tumor was documented by magnetic resonance imaging, scintigraphy, and histopathology. [37]


Other Tests

A review of dermoscopy patterns in congenital nevi found that most nevi demonstrate a reticular, globular, or reticuloglobular pattern. The findings varied with age and the anatomic location of the nevus, with the globular pattern found more often in younger children and the reticular pattern found in patients aged 12 years or older. [38]  Although valuable in melanoma, genetic testing of congenital melanocytic nevi is probably unnecessary. [39]


Histologic Findings

Because of the increased risk of melanoma associated with congenital nevi, attempts have been made to distinguish congenital nevi from acquired nevi on the basis of histology. Distinguishing histologic features include (1) involvement by nevus cells of deep dermal appendages and neurovascular structures (including hair follicles, sebaceous glands, arrector pili muscles, and within walls of blood vessels), (2) extension of nevus cells to deep dermis and subcutaneous fat, (3) infiltration of nevus cells between collagen bundles, and (4) a nevus cell–poor subepidermal zone. [40, 41, 42] Note the images below.

The photomicrograph shows a symmetrical broad prol The photomicrograph shows a symmetrical broad proliferation of melanocytes in the papillary and reticular dermis with maturation with progressive descent; splaying between collagen bundles; and permeation of muscles of hair erection, blood vessels, and adnexa (hematoxylin and eosin stain, 20X magnification).
Higher-power view of the previous image (hematoxyl Higher-power view of the previous image (hematoxylin and eosin stain, 40X magnification).

In contrast to congenital nevi, acquired nevi are usually composed of nevus cells that are limited to the papillary and upper reticular dermis and do not involve the appendages. One study showed the cellularity and pigment production of congenital melanocytic nevi in 21 patients decreased with age, with the histological pattern and extension in depth remaining stable. [43]