Hydatidiform Mole

Definition:

Hydatidiform Mole is one of the most common form of Gestational Trophoblastic Disease, but a benign one.

Epidemiology:

It is one of the most common complications experienced during pregnancy and occurs in every 1,000-2,000 of pregnancies. It can occur in any pregnant woman of any age, but high incidence has been recorded among pregnant teens, and pregnant woman between the ages of 40-50 years. It is more common in Asian countries.

Pathogenesis: 

Rarely, moles co-exist with a normal pregnancy (co-existant molar pregnancy), in which a normal fetus and placenta are seen separate from the molar gestation.
 A hydatidiform mole can either be complete or partial. The absence or presence of a fetus or embryo is used to distinguish complete moles from partial moles. Complete moles are associated with the absence of a fetus and partial moles usually occur with an abnormal fetus or may even be associated with fetal demise.
Ninety percent of complete hydatidiform moles have a 46XX diploid chromosomal pattern. All the chromosomes are derived from a single sperm in 90% or less likely two sperms, suggesting fertilization of a single egg that has lost its chromosomes.
With partial moles, the karyotype is usually triploid (69XXY): the result of fertilization of a normal egg by two sperm, one bearing a 23X chromosomal pattern and the other a 23Y chromosomal pattern.
 Location:
Complete hydatidiform moles usually occupy the uterine cavity and are rarely located in fallopian tubes or ovaries.
The chorionic villi are converted into a mass of clear vesicles that resemble a cluster of grapes.
Laboratory Markers:
In the classic case of molar pregnancy, quantitative analysis of beta-HCG shows hormone levels in both blood and urine greatly exceeding those produced in a normal pregnancy at the same stage.

Diagnosis:

Ultrasound
Complete Mole
>Enlarged Uterus
>Solid collection of echoes alternating with numerous 3-10mm anechoic spaces known as SNOWSTORM APPEARANCE or BUNCH of GRAPES
>  Normal Interface between myometrium and abnormal trophoblastic tissue
> No Identifiable fetal tissue or gestational sac seen
> May show high velocity, low impedance flow on color doppler.

 >The molar tissue demonstrates the bunch of grapes sign which represents hydropic swelling of trophoblastic villi.
> Ovarian theca lutein cyst may be seen bilaterally in 25-60% of cases
Partial Mole
>Placenta is enlarged and contains areas of multiple, diffuse anechoic lesions
>A fetus with severe structural abnormalities or growth restriction, oligohydramnios or a deformed gestational sac may be noted.
>Colour Doppler interrogation may show high velocity, low impedance flow.
> Ovarian theca lutein cyst may be seen bilaterally in 25-60% of cases
 MRI
MRI shows heterogenous endometrial thickening with T2 hyperintense areas. MRI is indicated in aggressive gestational trophoblastic disease to look for myometrial invasion and pathologically dilated endometrial, myometrial, or parametrial vessels.
CT
A CT scan usually demonstrates a normal-sized uterus with areas of low attenuation, an enlarged inhomogeneous uterus with a central area of low attenuation, or hypo-attenuating foci surrounded by highly enhanced areas in the myometrium.

Complications:
A complete mole can progress to invasive mole (~15%) or to gestational choriocarcinoma (~7%).

Complete Mole

 

Partial Mole