Yolk sac tumor with a unique uniform hepatoid pattern histology.

Background: Yolk sac tumors (YST) exhibit several different histological subtypes and the mechanisms of cellular differentiation and prognosis of each subtype remain unknown.
Results: We report two infants with sacrococcygeal YST; one represented a typical histological subtype and the other showed a hepatoid subtype with uniform histology. The isoform of alpha-fetoprotein (AFP) in the patient with the hepatoid pattern was examined by lectin-affinity immunoelectrophoresis and represented as a YST, but not hepatocellular, subtype. The patient with typical YST responded well to VAB-6 combination chemotherapy. However, this regimen was only partially effective to the patient with the pure hepatoid histological subtype, and an etoposide with ifosfamide and cisplatin (VIP) regimen as a salvage chemotherapy combined with complete tumor resection was useful to achieve complete remission (CR). Both of the patients have been in CR for more than four years.