A 23-year-old man first presented to an outlying hospital with a 3-week history of anosmia and mild proptosis in his left eye. Computed tomography (CT), revealed an isodense and wellcircumscribed mass arising from the left ethmoid sinus . Erosions of the lamina papyracea was observed that was extending into the maxillary sinus and the left orbit while compressing the left medial rectus muscle. Extension to the crista was noted. Subsequent T2-weighted magnetic resonance imaging (MRI) showed a mass in the left ethmoid sinus . Alveolar rhabdomyosarcoma (RMS) was diagnosed following endoscopic biopsy by an ENT specialist, and immunohistochemistry of the mass. The patient underwent chemotherapy with vincristine, doxorubicin, and cyclophosphamide alternating with ifosfamaide plus etoposide (VEC+IE), followed by 25 fractions of radiotherapy.Maintenance chemotherapy achieved one-year remission but eventually new symptoms emerged. He was referred to our ophthalmology department. A reddish medial canthal mass was present in the left eye with periorbital puffiness, injection of the nasal conjunctiva and diffuse punctate epithelial erosions. The mass in the medial orbital wall was relatively large (30 mm in diameter), palpable, and non-mobile. The globe was displaced laterally. There was slight left gaze diplopia and limitation of abduction and adduction. Other ocular examinations were normal and his corrected visual acuity was 20/20 OU. Spiral axial and coronal CT of the orbit [Table /Fig-1c,d] revealed an extraconal mass in the medial orbit of the left eye, extending posteriorly, causing dystopia of the globe, and compressing the medial rectus muscle. Remarkably, the ethmoid and maxillary sinuses were clear. An extensive preoperative metastatic workup was negative. Inferior transconjunctival orbitotomy was performed to obtain an incisional biopsy. A whitish avascular tumour was found. Immunohistochemical staining for actin and myogenin was positive [Table/ Fig-2]. Round myoblasts with abundant eosinophilic cytoplasm were identified. With a diagnosis of recurrence of alveolar RMS, the patient received his second round of chemoradiotherapy. At the 3-month follow-up visit, the mass was reduced in size by 80% and disappeared completely in the weeks following the treatment. However, he had developed dry eye Alveolar rhabdomyosarcoma (RMS) is a primitive, malignant, round cell neoplasm derived from mesenchymal tissue that exhibits partial skeletal muscle differentiation. We describe a rare case of alveolar RMS of ethmoid sinus, recurring as an orbital mass. A 23-year-old man with the chief complaint of anosmia and mild proptosis was diagnosed with RMS of the left ethmoid sinus and orbit following an endoscopic biopsy of the mass. He was treated with chemotherapy and radiotherapy. At 12 months after diagnosis, while still on maintenance chemotherapy, he presented to our eye hospital with a large medial canthal mass and lateral globe displacement. Orbital computed tomography revealed an extraconal mass in the medial orbit of the ...