* Address correspondence to Richard Jaffe, MD, Department of Obstetrics and Gynecology, University of Illinois at Chicago, 840 South Wood St., Chicago, IL 60612-4324 Tel: 312-996-7300, Fax: 312-996-4238, ¶Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, Israel

Synonyms: Incomplete molar gestation, partial triploid mole.

Prevalence: 0.1-1:10,000 of all pregnancies.

Definition: Focal hydropic swelling of chorionic villi with trophoblastic hyperplasia and identifiable embryonic or fetal tissues.

Etiology: Abnormal fertilization.

Pathogenesis: Fertilization of a normal (haploid) ovum by two normal (haploid) sperms or fertilization of a normal ovum by an abnormal (diploid) sperm. All configurations (XXX, XXY, XYY) have been found.

Associated anomalies: As virtually all partial moles are triploid, anomalies of all major systems have been found. They include anomalies of the CNS, the heart, lungs, skeleton and genitalia. All fetuses show intra-uterine growth retardation.

Differential diagnosis: Twin gestation with one fertilized ovum undergoing molar degeneration and hydropic changes in a missed abortion.

Prognosis: Most die in utero during first or early second trimester and if born alive they die within a few hours.

Recurrence risk: Not known but probably none.

Management: Evacuation of pregnancy when diagnosis of partial triploid mole is done, as there are reports of persistent trophoblastic disease. Follow-up with serial bhCG.

MESH Aneuploidy-; Chromosome-Aberrations; Chromosome-Abnormalities-diagnosis; -genetics; Chromosome -Aberrations-genetics; Hydatidiform-Mole -classification, -diagnosis, -etiology, -genetics, -pathology; Placenta -pathology; Ploidies-; Polyploidy BDE 2400 MIM 23109 ICD9 630 CDC 758.586 (triploidy), 630.010 (embryonic mole)

Introduction

Partial moles account for 0.001-0.01% of all pregnancies, and all have severe chromosomal anomalies^1-3. It is well documented that some of these develop into persistent trophoblastic disease and may require major surgery and chemotherapy⁴. The majority of partial moles abort spontaneously in the first trimester, whereas only sporadic cases reach the second trimester, creating both a diagnostic and management dilemma.

Sonographic diagnosis with elevated serum human chorionic gonadotropin (hCG) levels and fetal karyotype have been the criteria for diagnosis of this condition. Recently, elevated maternal serum alpha-fetoprotein (MSAFP) levels have been reported in all cases of partial mole diagnosed in the second trimester⁵.

We hereby report an additional case of a partial mole diagnosed by the ultrasonic image and serum markers and discuss the appropriate clinical management.

Case report

A healthy 25-year-old Caucasian primigravida was referred for consultation at 16-weeks gestation due to a elevated MSAFP (3.8MoM). The pregnancy was well dated by a last menstrual period and a positive serum bhCG 3 days after her first missed period. There were no unusual findings on a pelvic examination. The serum b-hCG was 247000 mIu/ml. A sonographic examination employing a Sonoline SL-1 (Siemens AG, Holland ) revealed a viable 14-week fetus by biometry with no visible anomalies and normal amniotic fluid. The placenta was enlarged and had a molar appearance (Fig.1).

The patient had bilateral adnexal cysts. Percutaneous umbilical blood sampling (PUBS) was refused by the patient and an amniocentesis was performed. The karyotype revealed fetal triploidy (69XXY).

Amniotic fluid AFP and acetylcholinesterase were normal. By the time the karyotype was received, the patient was hypertensive with no other signs of pre-eclampsia. Extra-amniotic prostaglandin (PGF2) was instilled at a rate of 1 mg/hour at 20-weeks gestation. Thirty-six hours later, a 140g phenotypically normal fetus was expelled. The placenta weighed 490g and had the hydropic appearance of a molar placenta. The pathological examination of the placenta confirmed the diagnosis.

The maternal serum test for fetal erythrocytes was negative.

Weekly quantitative serum bhCG levels were obtained until negative 6 weeks after termination.

Discussion

Partial mole is a disease recognized as a distinct entity with morphological similarities to a complete mole. Cytogenetic studies have demonstrated that all pathologically proven partial moles have an abnormal karyotype^1-3,5,7. The majority (70-80%) of the triploid partial moles have a 69XXY karyotype, 69XXX is found in 20-25% and only in rare cases has the 69XYY karyotype been found.

Partial moles result from a paternal origin, whereas classic moles usually result from a maternal origin. With paternal triploidy, the conceptus results from fertilization of either two normal (haploid) spermatozoa or an abnormal (diploid) spermatozoa (fig. 2).

With maternal triploidy, fertilization results from penetration of a normal sperm into an ovum that has failed to undergo the reduction division. Growth retardation is a common finding, and present are often anomalies of head, heart, lungs, adrenals and other organs (Table I). These cases are non-molar and do not belong to the entity of partial moles.

Table 1: Anomalies associated with partial moles and triploid fetuses

Like complete moles, up to 10% of patients with partial moles may develop severe complications directly related to this condition⁴. The complications are myometrial invasion by persistent trophoblastic disease^8,9 as well as distant metastases to the lungs¹⁰. Complete moles usually present as early abortion, and the diagnosis is made early by the distinct sonographic image.

With partial moles the diagnosis is complicated by the fact that there is a living fetus, and the cystic changes of the placenta do not always lead to the diagnosis^11,12. Although serum bhCG levels are elevated in these cases, this test is not performed routinely if the level of suspicion on ultrasound examination is not great.

It is also important to realize that an ultrasonic image of a hydropic placenta can be detected in other conditions. These conditions are twin gestations with molar degeneration of one of the fetuses, and there have also been reports of partially hydropic placentas with normal viable fetuses. Lately, MSAFP has become a screening tool and is performed routinely in many countries. Initially it was performed to screen for neural tube defects but was found to be elevated in several fetal anomalies such as abdominal wall defects, cystic hygroma, congenital nephrosis and placental abnormalities^13,14. Some reports have described elevated MSAFP in triploid fetuses^5,6, and some of these cases had hydropic placentas. One of the explanations for this elevation is the breakdown of placental structure with leakage of fetal blood into the maternal circulation, an explanation that could be possible in the case of a partial mole¹⁵. Another possible explanation is an increase in placental permeability, causing the increase in maternal MSAFP in the presence of normal amniotic fluid AFP^5,16.

As was shown in this case, and others reported in the literature, in addition to a distinct sonographic image of the placenta, all partial moles have elevated levels of serum bhCG and MSAFP. It is therefore suggested that in all cases of elevated MSAFP a complete ultrasonic examination should be performed in addition to a serum bhCG if there are any signs of cystic hydropic changes in the placenta.

The prompt diagnosis will enable proper counseling and performance of invasive diagnostic procedures if indicated. Although karyotyping is the only means to arrive at a definite diagnosis, it has a major disadvantage. Amniocentesis will cause a 2-3 weeks delay of treatment and thereby increase the risk of early onset preeclampsia, which places the mother at unnecessary risk. The delay of definitive treatment may also increase the risk of persistent or metastatic disease. The triad of the specific ultrasonic image of the placenta along with the elevated levels of MSAFP and bhCG strongly suggests the diagnosis of partial mole, and a larger multicentric study may arrive at the conclusion that they are adequate for a definitive diagnosis.

References

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10. Szulman AE, Surti U. Patient with partial mole requiring chemotherapy. Lancet 1978;2:1099.

11. Wong LC, Ma HR. The syndrome of partial mole. Arch Gynecol 1984;234:161.

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13. Burton BK, Sowers SG, Nelson LH. Maternal serum alpha- fetoprotein screening in North Carolina: experience with more than twelve thousand patients. Am J Obstet Gynecol 1983;146:439.

14. Norgaard-Pedersen B, Bagger P, Bang J, et al. Maternal serum alpha-fetoprotein screening for fetal malformations in 20,062 pregnancies. Acta Obstet Gynecol Scand 1985;64:511.

15. Berkeley AS, Killackey MA, Cederquist LL. Elevated maternal serum alpha-fetoprotein levels associated with breakdown in fetal-maternal placenta barrier. Am J Obstet Gynecol 1983;146:859.

16. Perkes EA, Baim RS, Goodman KJ, Macri JN. Second-trimester placental changes associated with elevated maternal serum alpha-fetoprotein. Am J Obstet Gynecol 1982;144:935.