A Partial Hydatidiform Mole in an Ovarian Ectopic Pregnancy: An Exceptional Occurrence

Abstract

Background and Clinical Significance: Ovarian ectopic pregnancy (OEP) is a rare occurrence, and molar degeneration is even more exceptional. Differential diagnosis between a partial and complete hydatidiform mole is paramount as the complete type carries a higher risk of post-molar gestational trophoblastic neoplasia. Herein, we describe a case of a partial mole in an OEP (OPHM) with thorough investigations. Case Presentation: A 39-year-old woman presented at 6 weeks of amenorrhea with abdominal pain and vaginal bleeding. Ultrasound showed no intrauterine pregnancy, but an ovarian cyst suspicious for OEP. The patient underwent surgical removal of the cyst. Histological diagnosis was suspicious for OPHM with only one abnormal villous. Immunohistochemistry for p57^kip2 and fluorescent in situ hybridization (FISH) were not conclusive. STR-based (Short Tandem Repeat) molecular technique demonstrated the chromosomal asset of 69,XXX, confirming the diagnosis of OPHM. The patient was fully monitored for 1 year with periodic measurements of beta-hCG levels. After that period, the patient was in good health and disease-free. Conclusions: Histologically, ancillary techniques might not be sufficient to confirm the diagnosis of a hydatidiform mole, especially if the tissue available is scarce. In this case, STR has been demonstrated an effective tool in defining the chromosomal asset, even in paraffin-embedded samples.

Keywords: Short Tandem Repeat (STR); ovarian ectopic pregnancy; partial hydatidiform mole.

Figure 1

Right ovarian cyst at US: (A,B) iso-hypoechoic cyst with irregular profile of the ovarian parenchyma (red line). (C) Peripheral blood flow associated with a mild Swiss cheese appearance (yellow arrow).

Figure 2

Ovarian ectopic pregnancy: the submitted tissue was composed of villi and partially organized blood. One villous (bottom left) was suspicious for molar degeneration as presented an inner cistern and focal trophoblast proliferation (Hematoxylin and Eosin, 2 HPF).

Figure 3

Ovarian ectopic pregnancy: the cyst presented an outer layer made up of eosinophilic cuboidal cells consistent with a follicular cyst/early corpus luteum (Hematoxylin and Eosin, 20 HPF).

Figure 4

Immunohistochemistry for p57^kip2: in the suspected hydropic villous the marker was expressed in the cytotrophoblast, arising the suspicion of a partial mole (4 HPF).