Diagnostic ultrasound ( PDFDrive )

1078 PART IV Obstetric and Fetal Sonography
and partial), invasive mole, choriocarcinoma, and placental
trophoblastic tumor. 133
Hydatidiform Molar Pregnancy
Hydatidiform molar pregnancy is the most common and benign
form of gestational trophoblastic disease, with an incidence of
1 in 1000 pregnancies in North America. 134 he incidence is
much higher in the Asian population. here is an increased risk
in teenagers, in women older than 35 years of age, and in women
with a previous molar pregnancy. he risk also increases with
the number of previous spontaneous abortions. 135 Molar pregnancy
is characterized histologically by cystic (hydatidiform)
degeneration of chorionic villi, with absent or inadequate vascularization
and abnormal trophoblastic proliferation. Embryos
or fetuses are either absent or abnormal.
he most frequent presenting symptom is vaginal bleeding,
which occurs in more than 90% of cases. Passage of vesicles
(hydropic villi) through the vagina occurs frequently and is
considered speciic for the diagnosis of molar pregnancy. 136 he
uterus may be enlarged for dates, and there may also be rapid
uterine enlargement. Medical complications include pregnancyinduced
hypertension, hyperemesis gravidarum, preeclampsia,
and hyperthyroidism. he routine use of ultrasound for any
woman with bleeding in pregnancy allows for early diagnosis,
and few women in current practice show the classic features of
hyperemesis and preeclampsia. 137
Serum β-hCG levels in molar pregnancy are abnormally
elevated, usually greater than 100,000 mIU/mL. he ovaries may
be greatly enlarged in complete molar pregnancy by multiple,
bilateral theca lutein cysts. hese are large, usually multilocular,
and may undergo hemorrhage or torsion and can be a source
of pelvic pain. heca lutein cysts are most marked when trophoblastic
proliferation is severe, and when hCG is elevated.
hey are seen much less oten in the irst trimester. 138,139
Molar pregnancy is treated by uterine evacuation, which
is adequate in most patients. Approximately 80% of complete
moles and 95% of partial moles will subsequently follow a
benign course. 136,140 However, accurate diagnosis and classiication
of molar pregnancy are important because of the risk
of persistent trophoblastic neoplasia (PTN). he American
College of Obstetrics and Gynecology currently recommends
follow-up testing for hCG for 6 months ater levels become
undetectable. 141
Hydatidiform molar pregnancy is classiied as either complete
molar pregnancy or partial molar pregnancy on the basis of
cytogenetic and pathologic features.
Complete Molar Pregnancy
Complete molar pregnancy is characterized by a diploid karyotype
of 46,XX in 80% to 90% of cases, with the chromosomal
DNA being exclusively paternal in origin. 142 his occurs when
an ovum with absent or inactive maternal chromosomes is fertilized
by a normal haploid sperm. Occasionally, fertilization of
an empty ovum by two haploid sperm results in a 46,XY pattern. 135
As the embryo dies at an early stage, no fetal parts are seen. 142
he placenta is entirely replaced by abnormal, hydropic chorionic
villi with excessive trophoblastic proliferation.
he classic sonographic features of complete molar pregnancy
include an enlarged uterus with a central heterogeneous echogenic
mass that expands the endometrial canal. he mass contains
multiple cystic spaces of varying size, representing the hydropic
villi (Fig. 30.38). hese cystic spaces may vary in size from a few
millimeters to 2 to 3 cm. In the second trimester, TAS diagnosis
is highly accurate. he second trimester appearance typically
presents as an echogenic mass containing multiple tiny cysts
due to the hydropic villi in what used to be termed a “snowstorm”
pattern. However, with the higher frequencies now used the
“snowstorm” has become a “bunch of grapes.”
In the irst trimester, molar pregnancies have a variable
appearance on ultrasound, sometimes appearing as a predominantly
solid, echogenic mass or even as an intrauterine luid
collection because tiny hydropic villi may not be adequately
resolved (Fig. 30.39). In these cases, a molar pregnancy may not
be able to be diferentiated from a miscarriage.
Partial Molar Pregnancy
Partial molar pregnancy has a triploid karyotype of 69,XXX,
69,XXY, or 69,XYY and is also referred to as “triploidy.” Most
partial moles have one set of maternal chromosomes and two
sets of paternal chromosomes, resulting from fertilization of a
normal ovum by two haploid sperm. Triploidy of maternal origin
is not associated with gestational trophoblastic disease. 143 Pathologically,
partial molar pregnancy has well-developed but generally
anomalous (triploid) fetal tissues. Hydropic degeneration of
placental villi is focal, interspersed with normal placental villi
(Fig. 30.40).
Triploidy is discussed in more detail in Chapter 31.
Placental hydropic degeneration (unrelated to trophoblastic
neoplasia) may also show similar sonographic features. Hydropic
degeneration occurs frequently in irst-trimester abortion of any
cause. he associated cystic spaces may be diicult or impossible
to diferentiate from an early mole. herefore in cases with
equivocal ultrasound features, the products of conception should
be carefully evaluated to avoid missing a hydatidiform mole.
Recent studies have shown that sonography is much more
accurate in diagnosing complete molar pregnancy than partial
molar pregnancy. Kirk et al. 144 evaluated sonography in the irst
trimester and found an accuracy of 95% for the diagnosis of
complete mole and 20% for partial mole, with an overall accuracy
for hydatidiform mole of 44%. In 859 pathologically diagnosed
hydatidiform moles, Fowler et al. 145 found that sonography
performed in the irst and early second trimester had a similar
44% overall accuracy and an accuracy of 79% and 29% for
complete and partial moles, respectively. Also, the sonographic
detection rate improved ater 14 weeks’ gestation.
Coexistent Hydatidiform Mole and Normal Fetus
In complete moles, an embryo or fetus is absent except in the
rare event of a coexistent twin pregnancy. hese twin pregnancies
with an apparently normal fetus and a hydatidiform mole are
uncommon, with an estimated incidence of 1 in 20,000 to 100,000
pregnancies. 146,147 It is diferentiated from a partial molar pregnancy
by identifying a normal-appearing fetus with a corresponding
normal placenta adjacent to a mass of placental tissue that