Diagnostic ultrasound ( PDFDrive )

CHAPTER 22 The Scrotum 823
FIG. 22.4 Mixed Tumor. Transverse scan of coexistent solid masses—
a mixed germ cell tumor (M) and a seminoma (S).
Seminoma. Seminoma is the most common pure, or single
cell–type, germ cell tumor in adults, accounting for 35% to 50%
of all germ cell neoplasms. 20,30 It is also a common component
of mixed germ cell tumors, occurring in 30% of these tumors.
Seminomas tend to occur in slightly older patients than do other
testicular neoplasms, with a peak incidence in the fourth and
ith decades, and they rarely occur before puberty. 3,42,43 hey
are typically conined within the tunica albuginea at presentation,
with approximately 25% of patients having metastases at diagnosis.
As a result of the radiosensitivity and chemosensitivity of the
primary tumor and its metastases, seminomas have the most
favorable prognosis of the malignant testicular tumors. A second
primary synchronous or metachronous germ cell tumor occurs
in 1% to 2.5% of patients with seminomas (Fig. 22.4).
Seminoma is the most common tumor type in cryptorchid
testes. Between 8% and 30% of patients with seminoma have a
history of undescended testes. 29,43 he risk of a seminoma developing
is substantially increased in an undescended testis, even ater
orchiopexy. Patients with a normally located but atrophic testis
have an increased risk of seminoma (Video 22.1). here is also
an increased risk of malignancy developing in the contralateral,
normally located testis. herefore sonography is oten used to
screen for an occult tumor in both testes ater orchiopexy.
Seminomas range from a small, well-circumscribed lesion to
large masses replacing the testis. Macroscopically, cellular
morphology resembles that of primitive germ cells, which are
relatively uniform. 25 he sonographic features of pure seminoma
parallel this homogeneous macroscopic appearance. Pure seminomas
usually have predominantly uniform, low-level echoes
without calciication, and they appear hypoechoic compared with
normally echogenic testicular parenchyma (Fig. 22.5). 44 Larger
tumors may have a more heterogeneous appearance. In rare cases,
seminomas become necrotic and appear partly cystic on sonography
(Fig. 22.5I).
Nonseminomatous Germ Cell Tumors. NSGCTs include
embryonal carcinomas, teratomas, yolk sac (endodermal sinus)
tumors, choriocarcinomas, and mixed germ cell tumors. hese
tumors occur more oten in younger patients than do seminomas,
with a peak incidence during the latter part of the second decade
and the third decade. hey are uncommon before puberty and
ater age 50. Approximately 70% of NSGCTs produce hormonal
markers. 45 Up to 60% of germ cell tumors are mixed germ cell
tumors, composed of at least two diferent cell types. 20,46 Pure
NSGCTs are rare and occur more oten in the pediatric population.
20 he sonographic appearance of NSGCTs relects the
histologic features and relative proportions of each component,
although as a group these tumors are more heterogeneous than
seminoma, demonstrating irregular margins, echogenic foci, and
solid and cystic components (Fig. 22.6). hese malignancies are
more aggressive than seminomas, frequently invading the tunica
albuginea and resulting in distortion of the testicular contour
(see Fig. 22.6). Approximately 60% of NSGCTs have metastatic
involvement at presentation. 46
Mixed germ cell tumors are the most common germ cell
tumors, constituting up to 60% of all germ cell tumors. hey
contain nonseminomatous germ cell elements in various combinations.
Seminomatous elements may also be present but do not
inluence prognosis or treatment. 47 Embryonal carcinoma is the
most common component, although any combination of cell
types may occur. Imaging features are variable, relecting the
diversity of this group of tumors. Nonseminomatous tumors are
not as radiosensitive as seminomas. Embryonal carcinoma is
composed of primitive anaplastic cells that resemble early
embryonic cells. It is present in 87% of mixed germ cell tumors,
but in its pure form it is rare, accounting for only 2% to 3% of
testicular germ cell neoplasms (Fig. 22.6C). 48 As with other
NSGCTs, embryonal cell tumors occur in younger patients than
seminomas do, with a peak incidence during the latter part of
the second and third decades. he sonographic features of pure
embryonal cell carcinoma are nonspeciic, especially in children,
in whom the only inding may be testicular enlargement without
a deined mass. 36,49
Totipotent germ cells that diferentiate toward extraembryonic
fetal membranes give rise to yolk sac tumors, or endodermal
sinus tumors. Yolk sac tumors are the most common germ cell
tumor in infants younger than 2 years, accounting for 80% of
childhood testicular neoplasms. 49 Yolk sac tumor is rare in its
pure form in adults, although it is present in 44% of adult cases
of mixed germ cell tumor (Fig. 22.6D). 20 Yolk sac tumor is
associated with elevated levels of α-fetoprotein in greater than
90% of infants. Teratomas constitute 5% to 10% of primary
testicular neoplasms. hey are deined according to the World
Health Organization (WHO) classiication on the basis of the
presence of derivatives of the diferent germinal layers (endoderm,
mesoderm, and ectoderm). Histologically, teratomas can be
divided into mature and immature. he peak incidence is in
infancy and early childhood, with another peak in the third
decade of life. In infants and young children, teratomas are the
second most common testicular tumor ater yolk sac tumor and
are considered benign, even when they are histologically immature.
43,50,51 Postpubertal testicular teratomas are malignant and