A rare case of extraskeletal Ewing's sarcoma/primitive neuroectodermal tumor developing in maxillary sinus of an old patient.

Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) family of tumors is an uncommon group of malignant neoplasms that may present in both skeletal and extraskeletal sites. PNET outside the central nervous system is called peripheral PNET (pPNET) developing from migrating embryonal cells of the neural crest. Very few cases of pPNET of the maxilla are reported in English literature. These tumors may be difficult to diagnose due to their primitive morphology. These tumors occur predominantly in infancy or early childhood. The occurrence of extraskeletal ES/PNET in the maxillary sinus in an old age is very rare. We report a case of extraskeletal ES/PNET developing in maxillary sinus in a 60-year-old woman. The ES/PNET should be included in the differential diagnosis of a small round cell tumor and immunohistochemical analysis with a panel of immunomarkers should be done for correct diagnosis and proper treatment.