A rare case of peripheral primitive neuroectodermal tumor (PNET) is reported. A 
68-year-old woman complaining of lumbago was admitted to our hospital. Diagnosis 
was made based on pathological findings characterized by Homer Wright-type 
rosettes. Ultrastructural examination showed the presence of neurosecretory 
granules and short cytoplasmic processes, which were highly suggestive of neural 
differentiation. Chromosomal analysis of the neoplastic cells revealed 
translocation (11;22)(q24;q12), which is often found in Ewing's sarcoma and 
Askin tumor. These results strengthen the hypothesis of a common histogenesis 
for these small round cell tumors, and suggest common oncogenesis for these 
neoplasms.