Summary:Alveolar rhabdomyosarcoma (RMS) has a predilection for the deep soft tissues of the extremities and mainly occurs in children. Although the tumor may originate in other sites, such as the nasal cavity or paranasal sinus, invasion of the orbit is unusual. We describe the clinicopathological features of 2 cases of alveolar RMS of the nasal cavity or paranasal sinus in adult patients with orbital extension. These cases of alveolar RMS of the nasal cavity or paranasal sinuses are described in 2 men, both in the third decade of life. These patients were evaluated with radiological studies. The histological diagnosis was confirmed by immunohistochemical methods. Treatment consisted in a combination of chemotherapy and radiation therapy following excisional biopsy. Alveolar subtype RMS is an extremely aggressive neoplasm that rarely presents in the orbit or paranasal sinuses of adults but should be considered in the differential diagnosis of tumors with this localization. Myoglobin, Myo D1, and myogenin seem to be the most specific markers for RMS.