Askin tumor is a malignant small round cell tumor that originates from the thoracopulmonary region, usually observed in young subjects. We report a case of askin tumor in a 11 year-old men, who had in his past history a surgery for hydatid cyst of the liver, actually hospitalised for right pulmonary upper lobe mass of the lung. After resection of the mass, the pathological exam confirmed the diagnosis of primitive neuroectodermal tumor (PNET). An adjuvant treatment (radiotherapy and chemotherapy) was done; the patient died 11 months after surgery. Askin tumor is an exclusion diagnosis not always readily made.