Placental metastasis from maternal primitive neuroectodermal tumor.

The occurrence of placental metastasis from maternal primitive neuroectodermal tumor (PNET) is extremely rare. A 33-year-old woman at 33 weeks' gestation was admitted to the hospital. She died of the disease on hospital day 28 because the unresectable tumor was located over a wide area of the retroperitoneum. A neonate was delivered by a caesarean section without evidence of disease and has survived to 1 year of age. Pathologically, the tumor consisted of monotonous small round cells with a high nuclear cytoplasmic ratio, including several pseudorosettes and Homer-Wright-type rosettes. On immunohistochemical examination, the tumor cells were positively stained for neuron-specific enolase. Microscopically, the placenta showed intervillous metastasis from the maternal PNET. This case may be the first one of placental metastasis from PNET ever reported in the literature.