Ewing's sarcoma/primitive neuroectodermal tumour occurring in the maxillary sinus.

A 12-year-old boy complained of swelling of the left cheek. Fiberscopic examination revealed the presence of a soft reddish mass in the middle meatus of the left nostril. CT scan showed a large mass completely filling the left maxillary sinus. The lesion originated from the maxillary sinus and extended to the middle nasal meatus; bone destruction and invasion of the subcutaneous tissue of the cheek were noted. T2-weighted MRI images revealed a heterogeneous signal in the left maxillary sinus. Under general anaesthesia, biopsies were obtained through an intraoral incision. On pathology, atypical cells containing irregular nuclei with scanty cytoplasm were noted. The tumour cells were strongly positive for CD99 and reacted weakly with NSE however the cells were negative for synaptophysin, LCA and cytokeratin on immunohistochemical examination. Based on these findings, the tumour was diagnosed as a Ewing's sarcoma/primitive neuroectodermal tumour. The patient was treated with radiotherapy and combination chemotherapy; subsequently, the tumour's size decreased markedly. After 20 months of follow-up, the patient showed no evidence of local tumour growth or metastasis.