Hydatidiform mole is also called as vesicular mole is a benign neoplasm of the chorion with malignant potential. It is due to the cystic degeneration of the chorionic villi, that results in the death of the fetus and the conversion of chorionic villi into a large number of vesicles varying in size from a pea to a large-sized grape. They resemble hydatid cysts, and hence the name hydatidiform mole. In a complete hydatidiform mole, there are no fetal blood vessels seen in the villi and there is no evidence of existence of the fetus. In a partial mole, there is focal trophoblastic proliferation with cystic degeneration mixed with areas of normal chorionic villi A normal or abnormal fetus may be present.

Hydatidiform Mole

INCIDENCE

There is a wide geographical variation. It is most commonly found in South Asian countries. Hydatidiform mole develops in approximately 1 in 1000 pregnancies in the United States and Europe. In India there are different reports from different regions but is found to be more frequent than in the Western countries.

RISK FACTORS

1) Age: There is a relatively high frequency of hydatidiform mole among pregnancies at the beginning or end of the childbearing period.

2) Previous molar pregnancy: Recurrence of hydatidiform mole is seen in about 1 to 2 per cent of cases. With a previous molar pregnancy, the risk of a repeat molar pregnancy is increased 4-5 times.

3) Genetic factors: Cytogenetic studies of complete molar pregnancies have identified the chromosomal composition most often to be 46 XX, with the chromosomes completely of paternal origin (Fig. 16.8). Typically, the ovum has been fertilised by a haploid sperm, which then duplicates its own chromosomes after meiosis, and thus the chromosomes are homozygous. Occasionally, the chromosomal pattern in a complete mole may be 46 XY, that is, heterozygous due to dispermic fertilisation. The majority of complete moles are diploid whereas most partial moles are triple.

PATHOLOGY

Microscopic examination of hydatidiform mole shows that the villous pattern is maintained. There is marked proliferation of both syncytiotrophoblasts and cytotrophoblasts. Marked edema of the stromal tissue is seen. The trophoblasts secrete fore hCG than in normal pregnancy. The ovaries contain multiple theca-lutein cysts which result from overstimulation of lutein elements by large amounts of chorionic gonadotrophin. Clinical Features

1) Bleeding following a period of amenorrhea:-

There is usually a period of amenorrhea followed by intermittent or continuous bleeding. There may be only spotting at times and it may last for weeks. In between, there may be a sero-sanguineous discharge. Along with the bleeding, sometimes bits of tissue containing vesicles are passed per vaginum and an inspection of the material may clinch the diagnosis. Severe hemorrhage is sufficient to produce shock and collapse may occur.

2)Hyperemesis gravidarum:

In a few women, there may be excessive vomiting resulting in dehydration

3) Signs of preeclampsia:

Hypertension, albuminuria, edema prior to 20th week of pregnancy should raise suspicion of molar pregnancy. Even eclampsia has been observed in molar pregnancy.

4) On general physical examination:-

The patient may be pale and mildly anemic. Blood pressure may be raised with associated albuminuria.

5) On abdominal palpation:-

The uterus may be enlarged more than the period of gestation. The characterstic boggy feel of the uterus is suggestive of a molar pregnancy. Fetal parts are not palpable and fetal heart sounds are not heard.

6) Vaginal examination:-

may reveal the absence of ballottement and the presence of enlarged cystic ovaries.

DIAGNOSIS

If the patient has already started the process of expulsion and vesicles are identified, the diagnosis is easy. In women who have not started to expel the products but in whom the clinical features are suggestive of a molar pregnancy, an ultrasound examination will help in confirming or ruling out the diagnosis (Fig. 16.9). In/molar pregnancy/ultrasound will show a snowstorm appearance and the absence of any fetal parts. Serum hCG level is higher than expected for the period of gestation.

TREATMENT

Treatment of hydatidiform mole consists of two phases:

1) Immediate evacuation of the mole

2) Subsequent follow-up for detection of persistent trophoblastic proliferation or malignant change.

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