[Molecular pathological diagnosis of twin pregnancy with complicated genetical characteristics]

Objective: To investigate the molecular pathological diagnostic strategy of twin pregnancy(TP) with complex genetic characteristics, using p57 immunohistochemistry and short tandem repeat (STR) genotyping. Methods: Ten cases of TP with suspected hydatidiform mole(HM) according to pathological morphology were collected in Peking University Third Hospital from 2015 to 2019, and were subject to p57 immunohistochemistry, STR genotyping and follow-up. Results: The age of ten patients ranged 23 to 36 years, with an average of 29.5 years. Seven patients accepted assisted reproductive techniques in this conception. Three patients with "divergent" p57 staining pattern were diagnosed as TP with complete HM by STR, in which one had a persistent trophoblastic disease. The villi of five patients were consistently positive for p57, but the genotyping result was polyploid and suspicious as TP. Four of them showed excessive paternal alleles at more than 40% of the loci, suggesting that concomitant partial moles could not be excluded. One patient was diagnosed as TP without HM according to the maternal allelic predominance at all loci in villi. Two patients with p57 "divergent" and "discordant" staining villi were genotyped as TP with mosaic conception. Conclusions: The correct identification of p57 staining pattern and accurate interpretation of STR genotyping results are important in diagnosing TP. It may assist pathologists in making a definite or likely diagnosis of TP with complex genetic features to fulfill clinical triage strategies and contribute to formulate a reasonable follow-up approach.