Egg donor pregnancy: a potential pitfall in DNA genotyping diagnosis of hydatidiform moles

A 34-yr-old woman presented with missed abortion at 10 wk of estimated clinical gestational age and underwent dilation and curettage. Gross and microscopic evaluation of the uterine contents revealed the presence of mildly hydropic, dysmorphic chorionic villi, with occasional trophoblastic pseudo-inclusions. The morphologic features raised the suspicion for partial hydatidiform mole, and DNA genotyping was performed using the AmpFlSTR Identifiler PCR Amplification system. The chorionic villous tissue showed unique alleles - not present in the maternal decidual tissue - at 12 of the 15 short tandem repeat loci, and 8 loci showed 2 unique alleles, suggesting a diandric, paternal-only genome. In contrast, p57 immunohistochemistry demonstrated a normal staining pattern with positive nuclear staining in villous stromal cells and cytotrophoblasts. Review of the patient's medical records revealed that the pregnancy was conceived through in vitro fertilization with egg donor embryos, explaining the presence of unexpected alleles simulating a dispermic complete mole on DNA genotyping. This is the first case report illustrating that an egg donor pregnancy may mimic a complete hydatidiform mole on DNA genotyping.