A 66-year-old woman referred for right cheek swelling was found to have a soft mass filling the right nasal cavity. Computed tomography and magnetic resonance imaging showed a huge right maxillary sinus tumor with bone destruction. Biopsy showed the tumor to consist of small round atypical cells immunohistochemically positive for cytokeratin, EMA, synaptophysin, and CD99, but negative for desmin and chromogranin. The diagnosis was primitive neuroectodermal tumor. Chemotherapy followed by heavy charged particle radiotherapy shrank the tumor dramatically. She died of multiple lymph node, lung, liver, and bone metastasis.
