Diagnostic ultrasound ( PDFDrive )

582 PART II Abdominal and Pelvic Sonography
neoplasms, with 95% being benign cystic teratomas (dermoids).
he others, including dysgerminomas and endodermal sinus
(yolk sac) tumors, occur mainly in children and young adults
and are almost always malignant. Germ cell tumors are the most
common ovarian malignancies in children and young adults.
When a large, predominantly solid ovarian mass is present in a
girl or young woman, the diagnosis of a malignant germ cell
tumor should be strongly considered 163 (Video 16.8).
FIG. 16.17 Clear Cell Carcinoma in Endometrioma. TVS shows
a complex cyst with homogenous low-level internal echoes centrally
and solid nodules peripherally. See also Video 16.7
C
Cystic Teratoma
Cystic teratomas make up approximately 15% to 25% of ovarian
neoplasms; 10% to 15% are bilateral. hey are composed of
well-diferentiated derivatives of the three germ layers: ectoderm,
mesoderm, and endoderm. Because ectodermal elements generally
predominate, cystic teratomas are virtually always benign.
Cystic teratomas are frequently seen in the reproductive years
but can occur at any age and can be seen in postmenopausal
women. hese tumors may present as a palpable mass. Cystic
teratomas are usually asymptomatic and oten are discovered
incidentally during sonography. In approximately 10% of cases,
the tumor is diagnosed during pregnancy. 50 Torsion is the most
common complication, whereas rupture is uncommon, occurring
in 1% of patients and causing a secondary chemical peritonitis.
Malignant transformation is also uncommon, occurring in 2%
of patients, usually older women, 50 and is almost exclusively due
to squamous cell carcinoma. 28
Sonographically, cystic teratomas have a variable appearance
ranging from completely anechoic to completely hyperechoic.
However, certain features are considered speciic (Fig. 16.19).
hese include a predominantly cystic mass with a highly echogenic
mural nodule, the dermoid plug. 164 he dermoid plug usually
contains hair, teeth, or fat and frequently casts an acoustic shadow.
In many cases the cystic component is pure sebum (which is
liquid at body temperature) rather than simple luid. 165
Cystic Teratomas: Sonographic Features
FIG. 16.18 Transitional Cell (Brenner) Tumor in Wall of Mucinous
Cystadenoma. TAS shows a large, well-deined cystic mass (C) with
a solid hypoechoic mural nodule (arrow). Pathologic examination showed
a Brenner tumor within the wall of a large, mucinous cystadenoma.
usually serous or mucinous cystadenomas or cystic teratomas,
frequently in the ipsilateral ovary 161 (Fig. 16.18). Sonographically,
Brenner tumors are hypoechoic solid masses. Calciication may
occur in the outer wall. A cystic component is uncommon, but
when present, usually results from a coexistent cystadenoma. 156,162
Pathologically, transitional cell masses are solid tumors composed
of dense ibrous stroma. hey appear similar to ovarian ibromas
and thecomas and to uterine leiomyomas, both sonographically
and pathologically.
Germ Cell Tumors
Germ cell tumors are derived from the primitive germ cells of
the embryonic gonad. hey account for 15% to 20% of ovarian
Dermoid plug
“Tip of the iceberg” sign
Dermoid mesh
Mobile spherules (rare)
Fat-luid level
A mixture of matted hair and sebum is highly echogenic
because of multiple tissue interfaces, and it produces poorly
deined acoustic shadowing that obscures the posterior wall of
the lesion. his has been termed the “tip of the iceberg” sign 166
(Fig. 16.19B). Highly echogenic foci with well-deined acoustic
shadowing may arise from other elements, including teeth and
bone. Multiple linear hyperechogenic interfaces, oten described
as lines and dots, may be seen loating within the cyst and
have been shown to be hair ibers. 167 his is also considered a
speciic sign and has been referred to as the dermoid mesh 168
(Fig. 16.19G). A fat-luid or hair-luid level may also be seen
(Fig. 16.19D and E). In most cases, as in other lesions such as
endometriomas and hemorrhagic cysts, the dependent layer will
be more echogenic. However, in approximately 30% of dermoids,