A rare case of carcinosarcoma of the maxillary sinus with osteosarcomatous differentiation

A unique case of carcinosarcoma in the maxillary sinus is reported. A 47-year-old man visited our hospital with complaints of right nasal obstruction and bloody rhinorrhea. Examination revealed a hemorrhagic mass with necrosis in the maxillary sinus that infiltrated the right nasal cavity. Histologically, the tumor was composed of both carcinomatous and sarcomatous elements. Nests of squamous cell carcinoma and adenocarcinoma were scattered in the sarcomatous element with osteosarcomatous differentiation. No distinct demarcation between the two elements was observed and some spindle-shaped cells in the sarcomatous component were immunoreactive to epithelial markers by immunohistochemical staining. Although the histogenesis of carcinosarcoma remains unclear, the histologic pattern of the present case indicates the possibility that a multipotential cell, capable of both epithelial and mesenchymal differentiation, was the origin of the rare tumor.