Diagnostic ultrasound ( PDFDrive )

584 PART II Abdominal and Pelvic Sonography
Doppler evaluation of a benign teratoma may show peripheral
low, but malignancy should be considered if low is seen centrally
and/or within solid areas. Additional indings suggesting malignancy
include isoechoic branching structures within the lesion
and invasion into adjacent organs. 28
Struma ovarii is a teratoma composed entirely or predominantly
of thyroid tissue. It occurs in 2% to 3% of teratomas.
Color Doppler sonography detected central blood low in solid
tissue in four reported cases of struma ovarii, compared with
absent central blood low in benign cystic teratomas. 173 his is
likely caused by the highly vascularized thyroid tissue in struma
ovarii, compared with the avascular fat and hair found in benign
cystic teratomas. Although associated hormonal efects are rare,
sonography may be valuable in identifying a pelvic lesion in a
hyperthyroid patient when there is no evidence of a thyroid
lesion in the neck. 174
Immature teratoma is uncommon, representing less than
1% of all teratomas, and contains immature tissue from all three
germ-cell layers. It is a rapidly growing malignant tumor that
most oten occurs in the irst two decades of life. Sonographically,
the tumor usually presents as a solid mass, but cystic structures
of varying size may also be seen. 163 Calciications are typically
present.
Dysgerminoma
Dysgerminomas are malignant germ cell tumors that constitute
1% to 2% of primary ovarian neoplasms and 3% to 5% of ovarian
malignancies. 50 hey are composed of undiferentiated germ cells
and are morphologically identical to the male testicular seminoma.
Dysgerminomas are highly radiosensitive and have a
5-year survival of 75% to 90%. his tumor occurs predominantly
in women younger than 30 years and is bilateral in approximately
15% of cases.
Sonographically, they are solid masses that are predominantly
echogenic but that may contain small anechoic areas caused by
hemorrhage or necrosis 163 (Fig. 16.20). CT and MRI have shown
these solid masses to be lobulated with ibrovascular septa between
the lobules. 175 A report using color Doppler ultrasound in three
dysgerminomas showed prominent arterial low within the
ibrovascular septa of a multilobulated, solid, echogenic mass. 176
U
M
A
B
C
U
L
FIG. 16.20 Dysgerminomas in Three Young Women. (A)
Transverse TAS shows large, solid pelvic mass (M) adjacent to
the uterus (U). This appearance could be easily confused with a
uterine ibroid. (B) TVS shows large solid ovarian mass with thin
linear hyperechoic areas. (C) Transverse TAS shows large bilateral
ovarian masses with increased vascularity seen in the right-sided
tumor, which extends over the uterus (U). Note also the enlarged
left ovary (L) due to tumor. See also Video 16.8.