Heterotopic atypical trophoblasts mimicking ectopic choriocarcinoma coexistent with a viable intrauterine pregnancy: A diagnostic dilemma.

•Ectopic choriocarcinoma coexistent with viable IUP is rare but has been reported.•Atypical and proliferative trophoblasts are normal in an early conceptus.•Evaluation including MRI and CXR did not reveal metastatic choriocarcinoma.•IHC analysis for p57, molecular genotyping of DNA microsatellites was performed.•β-hCGs appropriately rose then plateaued; remainder of pregnancy was unremarkable.