Complete moles

Complete

hydatidiform mole • Complete hydatidiform mole (gross pathology) - Ganzer Fall bei Radiopaedia

Uthman, E. Complete hydatidiform mole (gross pathology). Case study, Radiopaedia.org. (accessed on 27 Oct 2022) https://doi.org/10.53347/rID-77910 • CC by-nc-sa 3.0 (modified)

Complete

hydatidiform mole • Complete hydatidiform mole - Ganzer Fall bei Radiopaedia

Patel, M. Complete hydatidiform mole. Case study, Radiopaedia.org. (accessed on 27 Oct 2022) https://doi.org/10.53347/rID-16188 • CC by-nc-sa 3.0 (modified)

Radiopaedia • CC-by-nc-sa 3.0 • de

A complete hydatidiform mole (CHM) is a type of molar pregnancy and falls at the benign end of the spectrum of gestational trophoblastic disease.

Epidemiology

A complete hydatidiform mole is the commonest type of gestational trophoblastic disease.

Pathology

Complete moles are characterized by the absence of a fetus or fetal parts (i.e. no embryonic tissues). There is a non-invasive, diffuse swelling of chorionic villi.

Chromosomal composition

Approximately 90% of complete hydatidiform moles have a 46XX diploid chromosomal pattern with ~10% having a 46XY composition. All the chromosomes are derived from the sperm, suggesting fertilisation of a single egg that has lost its chromosomes.

Markers

Serum beta HCG levels are markedly elevated, out of proportion to the pregnancy.

Radiographic features

Ultrasound

enlarged uterus
may be seen as an intrauterine mass with cystic spaces without any associated fetal parts
- the multiple cystic structures classically give a "snowstorm" or "bunch of grapes" type appearance.
may be difficult to diagnose in the first trimester
- may appear similar to a normal pregnancy or as an empty gestational sac
- <50% are diagnosed in the first trimester
bilateral theca lutein cysts may also be seen on ultrasound
color Doppler interrogation may show high velocity with a low impedance flow

CT

CT evaluation is not usually performed due to its low resolution for the uterine assessment. CT may show an enlarged uterus with areas of low attenuation, or hypoattenuating foci surrounded by highly enhanced areas in the myometrium.

MRI

MRI may demonstrate a heterogeneous mass with cystic spaces distending the uterine cavity. Fetal parts are notably absent. Uterine zonal anatomy is often distorted although a hypointense irregular myometrial boundary may be seen .

T1: there may be areas of high signal corresponding to foci of hemorrhage
T2: there is heterogeneous high signal from the cystic spaces
T1 C+ (Gd): often demonstrates intense enhancement due to hypervascularity

MRI may also demonstrate bilateral theca lutein cysts.

Treatment and prognosis

Suction and curettage are used for evacuation and are usually the routine treatment. Serial beta hCG levels are performed until it is no longer detectable on the assay, as it is the main indicator of residual disease.

A complete mole is itself benign but is considered a premalignant lesion. Degeneration into more invasive and malignant types of gestational trophoblastic disease can occur in ~10-20% of cases.