Microarray Findings of Intraplacental Choriocarcinoma: A Report of Four Cases

Introduction/Objective Gestational trophoblastic neoplasia (GTN) is a group of poorly understood diseases characterized by an abnormal and overtly malignant proliferation of trophoblastic tissue. Choriocarcinoma, which may also be nongestational in origin, is a particularly invasive and aggressive variant of GTN that is composed of a dimorphic trophoblast population. Many studies have attempted to define choriocarcinoma via various cytogenetic, molecular, and epigenetic means; however, the exact etiology and pathogenesis of this tumor remain unclear, in large part due to its rarity. Estimates of the incidence of choriocarcinoma range from 1 in 24,000 to 1 in 40,000 pregnancies. Intraplacental tumors are even less common with 62 reported cases and an estimated incidence of 1 in 160,000 placentas. In an effort to better understand the pathogenesis of this rare entity, four cases of choriocarcinoma (of which three are intraplacental and one is intrauterine occurring one year following an unremarkable pregnancy) diagnosed at our institution since 2010 were identified for chromosomal microarray. Methods DNA was extracted from formalin-fixed, paraffin-embedded blocks of four matched cases: tumor and normal placenta. Single nucleotide polymorphism (SNP) microarray analysis was performed to assess genomic copy number differences between the tumor and the placenta from which it arose (Infinium Global Diversity Array-8 v1.0 BeadChip with an I Scan System; Illumina, San Diego, CA). Analysis of a placenta not affected by tumor was also performed. Results Early partial data review demonstrates copy number aberrations in choriocarcinoma arising in placental tissue. Additional interpretation of the data is ongoing. Conclusion DNA chromosomal microarray analysis was performed to search for genomic copy number differences in between the tumor and the placenta from which it arose. Recent studies suggest gestational choriocarcinoma oncogenesis may differ from that of other malignancies, but this conclusion is based on a low number of recurrent DNA mutations. SNP microarray analysis may further refine the current understanding of the oncogenesis of gestational choriocarcinoma.