Alveolar rhabdomyosarcoma is an uncommon tumor. It is a rare malignancy in adults and rarely occurs in paranasal sinuses in those aged older than 50 years. This report describes a locally invasive and destructive alveolar rhabdomyosarcoma arising in the ethmoid sinus of a 57-year-old woman. The small round blue cell tumors are positive for myogenin by immunohistochemistry and have a karyotype of 45, XX, -5, -13, der(16)t(1;1) (q21;q13) by cytogenetic analysis. Fluorescence in situ hybridization demonstrated a complex translocation with break apart of the FKHR region, which supports a diagnosis of alveolar rhabdomyosarcoma. This report characterizes this tumor through microscopic and cyto-genetic analysis and emphasizes the importance of considering rhabdomyosarcoma in the differential diagnosis of small round cell tumors of the head and neck region in the middle-aged adults.