Page 37 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 2-10 Benign Growths

EPIDERMAL NEVUS
Lines of Blaschko. Epidermal nevi
often follow these embryological lines.
Epidermal nevi are benign epidermal hamartomatous
growths that most commonly occur as small plaques
but can be widespread and can have associated systemic
findings. Epidermal nevi have a tendency to follow the
embryologic lines of Blaschko. The lines of Blaschko
are well defined and follow a whorl-like pattern. The
reason why these lesions follow Blashko’s lines is
not fully understood, but it is probably caused by an
interruption of normal epidermal migration during
embryogenesis.
Clinical Findings: The epidermal nevus typically
manifests in childhood as a solitary linear plaque. Epi-
dermal nevi do not have a race predilection, and they
can be found equally in males and females. This type
of nevus is not melanocytic in nature; rather, it is com-
posed of a proliferation of keratinocytes. The nevus
initially has a smooth surface and develops a mamillated
or verrucal surface over time. Epidermal nevi appear to
occur most commonly on the head and neck region but
can occur anywhere. After puberty, the lesions do not
change dramatically. Most are flesh colored to slightly
hyperpigmented. If found on the scalp, an epidermal
nevus can mimic a nevus sebaceus and can be associated
with hair loss, but more commonly it does not cause
alopecia.
The epidermal nevus is usually small and slightly
linear. Some are large, encompassing the entire length
of an extremity, and still others cover a large percentage
of the body surface area. Rarely, there is intraoral
mucosal involvement. These larger epidermal nevi are
more likely to be associated with systemic findings, such
as underlying bone abnormalities. The most common
bony abnormality is shortening of the unilateral limb.
The epidermal nevus syndrome is a rare disorder asso-
ciated with a large or widespread epidermal nevus and
many systemic findings.
The epidermal nevus syndrome is made up of a con-
stellation of findings. These children often present with
neurological deficits, including seizures, and develop-
mental delay. They can have a multitude of bony abnor-
malities, cataracts, and glaucoma. The finding of a
widespread epidermal nevus in an infant should alert
the clinician to the possibility of this syndrome and the
need for a multidisciplinary approach to patient care.
Pathogenesis: The epidermal nevus is a hamartoma-
tous proliferation of the epidermal components. The
exact cause is unknown. These lesions are believed to
be caused by a developmental abnormality of the ecto-
derm. The epidermal nevus syndrome has not been Epidermal nevus, low power. Hyperkeratosis, Epidermolytic hyperkeratosis, low power. The
shown to have any appreciable inheritance pattern and acanthosis, papillomatosis, and basilar same architecture as an epidermal nevus is seen;
is believed to be sporadic in nature. The exact genetic hyperpigmentation are prominent. however, prominent vacuolar changes are
defect is unknown; it is most likely a result of genetic seen within the epidermis.
mosaicism. The involvement of fibroblast growth factor
has been studied, but no firm conclusions have been
made. These lesions do not show any abnormalities of
melanocytes. Treatment: Small, isolated epidermal nevi can be epi dermal nevi. Cryotherapy with liquid nitrogen has
Histology: The findings in this condition are all removed with shave removal technique. They have a been used successfully, but it may leave unsightly
located within the epidermis. Significant acanthosis and high rate of recurrence with this technique, but recur- hypopigmentation in darker-skinned individuals and
hyperkeratosis, with papillomatosis, predominates. A rence may take many years. The advantages of this should be used with caution.
variable degree of pigmentation is seen in the involved technique are that it is relatively easy, noninvasive, and Complete surgical excision is curative for small epi-
keratinocytes, but this is not a disorder of melanocytes, quick, and it provides an opportunity to histopatho- dermal nevi. However, it leaves a scar that may be more
and the number of melanocytes is normal. The granular logically evaluate the tissue for any evidence of noticeable than the nevus was. Laser resurfacing, derm-
cell layer is expanded. Many unique histological vari- epi dermolytic hyperkeratosis. The disadvantage of abrasion, and chemical peels have been used to help
ants of epidermal nevi have been described. shave removal is that it is appropriate only for small smooth out the appearance of epidermal nevi.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 23