Diagnostic ultrasound ( PDFDrive )

CHAPTER 22 The Scrotum 831
Epidermoid Cysts
An epidermoid cyst is an uncommon, benign, generally
well-circumscribed tumor of germ cell origin, representing
approximately 1% of all testicular tumors. hese tumors occur
at any age but are most common during the second to fourth
decades. 42 Usually, patients present with a painless testicular
nodule; one-third of the tumors are discovered incidentally on
physical examination. Difuse, painless testicular enlargement
occurs in 10% of patients. Pathologically, epidermoid cysts
are composed of keratinizing, stratiied, squamous epithelium
with a well-deined, ibrotic wall. Although the histogenesis of
epidermoid cysts is controversial, the current prevailing theory
is that these entities represent teratomas that have undergone
monodermal diferentiation. However, a complete absence of
mesodermal or ectodermal components and absence of intraepithelial
neoplasia, a histologic precursor of germ cell tumors,
brings this theory into question. Additionally, unlike germ cell
tumors, epidermoid cysts have an invariably benign course
without recurrence or metastatic disease following resection. 86
Squamous metaplasia of seminiferous epithelium or rete testis
is an alternative diagnosis. 87 hese benign lesions can be differentiated
from premalignant teratomas only through histologic
examination.
Sonographically, epidermoid cysts are generally well-deined,
round to ovoid, avascular masses and may be multiple or bilateral.
86 A characteristic whorled or laminated appearance, like
the layers of an onion skin, corresponds to the alternating layers
of compacted keratin and desquamated squamous cells seen
histologically 88-90 (Fig. 22.12D, Video 22.2). his appearance,
however, may not be pathognomonic because it is rarely seen
with teratoma. 91 Another typical appearance of an epidermoid
cyst is a well-deined hypoechoic mass with an echogenic capsule
that may be calciied (Fig. 22.12F). here may be central calciication,
giving a “bull’s eye” or target appearance. 86 Epidermoid
cysts may also have the nonspeciic appearance of a hypoechoic
mass with or without calciications and may resemble germ cell
tumors (Fig. 22.12E). Avascularity is a clue to the diagnosis. 89
Although the sonographic appearance is characteristic, it is not
pathognomonic, and histologic conirmation should be obtained
by a conservative testis-sparing approach with local excision
(enucleation). 92 MRI has been used to support the sonographic
diagnosis of epidermoid cysts as they have a target appearance
with low signal capsule. he layers of keratinizing material are
rich in water and lipid and can appear as areas of high signal
intensity on both T1- and T2-weighted imaging. 93,94
Abscess
Testicular abscesses are usually a complication of epididymoorchitis,
although they may also result from an undiagnosed
testicular torsion, testicular infarct, trauma, a gangrenous or
infected tumor, or a primary pyogenic orchitis. Infectious causes
of abscess formation are mumps, smallpox, scarlet fever,
inluenza, typhoid, sinusitis, osteomyelitis, and appendicitis. 95
A testicular abscess may cross the mesothelial lining of the tunica
vaginalis, resulting in formation of a pyocele or a istula to the
scrotal skin.
Most oten, sonography demonstrates an irregularly marginated,
hypoechoic or mixed echogenic intratesticular mass
(Fig. 22.13). Testicular abscesses have no diagnostic sonographic
features but can oten be distinguished from tumors on the basis
of clinical symptoms and short-term interval change.
In patients with acquired immunodeiciency syndrome
(AIDS), distinguishing an abscess from a neoplastic process may
be diicult on sonographic examination. Clinical indings may
A
B
FIG. 22.13 Testicular Abscesses. (A) Transverse gray-scale image shows typical hypoechoic intratesticular abscesses, which may be indistinguishable
from a tumor. However, heterogeneity of the parenchyma, skin thickening, and developing pyocele suggest that these masses represent
abscesses. (B) Transverse color Doppler image shows echogenic and hypoechoic areas in the intratesticular abscesses with increased vascularity
around the abscesses.