Clinical Case A 66 year old man presented to our ENT department with left chronic nasal obstruction and left jugual sweeling without pain. The left jugual fossea was enlarged with a firm and unlimited mass 40X25 mm. Testing of trjigeminal nerv (V) was normal. Nasal endoscopy showed deformity of left nasal lateral wall without endonasal tumor.Facial CT Scan revealed a soft tissue most of left maxillary sinus with osteolysis (anterior pars of sinus). RMN a low intensity (T1) intra sinusal mass enhancement after gadolinium .biological evaluation note normochromic anemia (hemoglobin 8, 9 g/dl) and a normal WBC and platelet count, blood glucose 1, 05 g/l. The rest of the patient’s workup liver and kinder function was negative. A Rouge Denker technique (sub labial) approach was choosed with tumor extirpation and medial maxillectomy.The diagnosis of mast cell sarcoma was confirmed after immunohistochemical who’s expressed CD117 and CD 68. Radiotherpy (50 Gy) has been proposed. The follow-up is well after 14 month later.