Peripheral primitive neuroectodermal tumour of the orbit.

Peripheral primitive neuroectodermal tumours (pPNETs) are a group of soft-tissue tumours of neuroepithelial origin that arise outside the central and sympathetic nervous system. Orbital location is infrequent, and to the best of the authors' knowledge only 16 cases have been reported in the literature. With this article, the authors report the demographics and clinical characteristics, diagnostic features, differential diagnosis, prognosis and therapeutic options of primary orbital peripheral primitive neuroectodermal tumour, based on their patients and on the cases reported in the literature to date. A differential diagnosis should be made with other small round cell tumours; immunohistochemical and ultrastructural techniques are essential for this purpose. Although bone invasion and extraorbital extension are possible, systemic metastases are uncommon in the cases of orbital pPNETs. Surgery has been the initial treatment in most cases; chemotherapy with or without radiotherapy is considered the best additional treatment. The orbital pPNET could be less aggressive than other forms of pPNETs, since most of the patients reported were alive after the follow-up period (at least 6 months).