Pure yolk sac tumors in genital and extragenital sites: study on three pedriatic cases, with cytological findings on two.

Cytopathological findings on three pedriatic gonadic-extragonadic pure yolk sac tumor are reported: the highly variable histological patterns (reticular, solid, festooning or pseudopapillary, polyvesicular vitelline), reflecting differentiation towards extraembryonic yolk sac structures, are not appreciated in cytologic samples. Since the tumor's cytologic spectrum is very broad, the most diagnostic differential difficulty with yolk sac tumor is adenocarcinoma. The presence of intracellular and extracellular hyaline globules, that are periodic acid-Schiff stain (PAS) positive and diastase resistant and correspond to alpha-fetoprotein production, alpha-fetoprotein positivity of the neoplastic cells; showing nuclear pleomorphism and vacuolated "bubbly" cytoplasm are the most consistent cytologic hallmarks of this neoplasm, which diagnosis would be confirmed by histologic, immunocytochemical and clinical findings.