Primary peripheral neuro-ectodermal tumor (pPNET) is a rare and very aggressive tumor that belongs to a small round cell tumor, and is most often located in the chest wall. PNET of the chest wall belongs to the Ewing sarcoma family because of their genotypic and phenotypic appearance, It can affect several organs, Pleural localization remains rare and little described in the literature. Here, we report a case of a particular localization of a pPNET. This is a 30-year-old patient who presented with chest pain on the right side, posterior irradiation, stage III dyspnea of MMRC and a dry cough, all progressing in a context of apyrexia and significant weight loss. .The chest X-ray showed complete opacification of the right hemi-thorax with deviation from the midline to the left side. Thoracic computed tomography reveals a large right pleural mass of cystic density containing multiple raised septa after injection of the PDC, pushing back the mediastinum to the left, the liver below, and the vascular structures of the neck above and inside which, however, remain permeable, associated a pleural effusion of moderate abundance, without other secondary localizations. The diagnosis of pleural Pnet was made on an echo-guided biopsy of the necrotic pleural mass. The patient was then transferred to the cancer center to start chemotherapy. We insist through this work on the rarity of the pathology, the diagnostic difficulties and the reserved prognosis.

Keywords : Peripheral primitive neuro-ectodermal tumor (PNET)  Pleural space  Necrotic pleural mass