Page 36 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 2-9 Integumentary System

Origin of pilosebaceous unit cysts

Infundibulum

Isthmus
EPIDERMAL INCLUSION CYST

Epidermal inclusion cysts are the most common benign
cysts derived from the skin. They are also known as Bulge area. This area
epidermoid cysts or follicular infundibular cysts. The contains the stem cells
name “sebaceous cyst” has been used to describe these Suprabulbar that re-form new hair. Epidermal inclusion cyst, sometimes
cysts, although this is a misnomer, because epidermal referred to as a sebaceous cyst. The
inclusion cysts are not derived from sebaceous epithe- upper cyst is red and inflamed.
lium. The cysts can occur anywhere on the body except The lower noninflamed cyst
the palms, soles, glans, and vermilion border. has a central punctum.
Clinical Findings: Most epidermal inclusion cysts
are subcutaneous nodules that vary in size from 5 mm
to more than 5 cm. They have no race predilection but
are seen more commonly in men than in women. Onset Bulb
most commonly occurs during the third decade of life.
The nodules characteristically have an overlying central
punctum. From this punctum, drainage of white,
cheese-like material, which represents a buildup of
macerated keratin debris, can occur. Most small epider-
mal inclusion cysts are asymptomatic, and they rarely
cause a problem. Low power. A well-
Larger epidermal inclusion cysts can become irri-
tated and inflamed. If the inflammation is severe circumscribed cyst
is seen within the
enough, the cyst wall ruptures. When the cyst contents dermis. The cyst lining
enter the dermis, the keratin sets off a massive inflam- is formed by stratified
matory reaction, which manifests clinically as edema, squamous epithelium,
redness, and pain. Once this has occurred, patients which contains a
often seek medical advice. granular cell layer.
The main differential diagnosis for a ruptured epi-
dermal inclusion cyst is a boil or furuncle. Ruptured A slight amount of
dermal inflammation
epidermal inclusion cysts are almost never infected, is seen surrounding
although infection can occur within a long-standing the cyst. Epidermal inclusion cyst
ruptured cyst that has not been treated. The main dif- arising at the site of scar
ferential diagnosis of an unruptured, noninflamed epi-
dermal inclusion cyst is a pilar cyst. Pilar cysts do not
have an overlying central punctum, and this is the
easiest means of differentiating the two cyst types. Pilar
cysts are also more common on the scalp. Milia are High power. The stratified
considered to be tiny epidermal inclusion cysts. squamous lining is better
Histology: The epidermal inclusion cyst is a true cyst appreciated in this high-
with an epithelial lining of stratified squamous epithe- power image. An intact
lium and an associated granular cell layer. The central granular layer is seen.
cavity is filled with keratin debris. The cyst is derived The cyst contents appear
from follicular epithelium. as wavy eosinophilic
Pathogenesis: The epidermal inclusion cyst is derived material.
from the infundibulum of the hair follicle. Epidermal
inclusion cysts occur as the result of direct implantation
of epidermis into the underlying dermis; from there,
the epidermal component continues to grow into the
cyst lining. Many researchers have looked at the roles
of ultraviolet light and human papillomavirus infection
in the etiology, but no definitive conclusions on either entire cyst wall. If a small portion of the cyst wall is left pungent odor. The resulting cyst cavity can be packed
have been drawn. behind, the cyst is likely to recur. or left open until the patient returns in 2 to 3 weeks
Treatment: Small cysts that are asymptomatic do Inflamed cysts should be treated initially with an inci- for definitive removal of the cyst lining by excision.
not need to be treated. One should advise patients sion and drainage technique. The region is anesthetized Intralesional triamcinolone is very effective in decreas-
not to manipulate or squeeze the cysts. Such trauma and then incised with a no. 11 blade. The resulting ing the inflammation and pain in these inflamed cysts.
could cause rupture of the cyst wall and set off an cheesy-white macerated keratin debris is removed with Long-standing cysts should be cultured and the patient
inflammatory reaction. Small cysts can be cured by a lateral pressure, and a curette is used to break apart given the appropriate antibiotic therapy based on the
complete elliptical excision, making sure to remove the internal loculations. The drainage material has a culture results.

22 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS