Choriocarcinoma is a rare, highly malignant trophoblastic tumor with gestational or, rarely, germ cell origin. Primary extragenital localization is extremely rare. This report describes a choriocarcinoma case clinically mimicking a primary renal cell carcinoma with multiplex pulmonary metastases. Differentiation from a sarcomatoid renal cell carcinoma with trophoblastic differentiation and identification of the exact origin, namely gestational or germ cell origin by molecular genetic methods is of great importance as it helps determine the prognosis and the most effective therapy of the disease. The Investigator Hexaplex ESS Kit was used for DNA polymorphism studies. This showed foreign alleles in the tumor DNA that confirmed the presence of paternal DNA and the gestational origin of the tumor.