IntroductionCarcinosarcoma is a highly malignant tumor characterized by dual malignant histologic differentiation of epithelial and mesenchymal components. The tumor is extremely rare in the sinonasal tract, with only 13 cases reported since 1957 in the literature.Presentation of caseWe report a case of a 55-year-old man with right-sided face pain revealed a mass in the right maxillary sinus and nasal cavity. A large incisional biopsy from the nasal cavity concluded the diagnosis of carcinosarcoma. The patient was treated with chemoradiation, but no significant effect was obtained. The patient died 4 months after initial examination.DiscussionIn our case, the patient consulted late with a large tumor which darkens his prognosis. According to some authors, this histological type of tumors is known by local recurrences and its lethal metastases. Prognosis is related to location, tumor size, the invasion and stage of disease. Wide surgical excision is the treatment of choice. Radiotherapy can be discussed in inoperable cases.ConclusionThis is an aggressive tumor, rapidly progressive with a poor prognosis. The management of this rare condition remains undetermined.