Unilateral Proptosis due to Orbital Metastasis of Paratesticular Leiomyosarcoma.

Paratesticular leiomyosarcomas are uncommon malignant tumours that originate from smooth muscle and show aggressive tumour behaviour due to a high incidence of local recurrence and distant metastasis. Orbital metastasis is also rare and associated with a poor prognosis. Clinical suspicion plays an essential role in the diagnosis of orbital leiomyosarcoma because of its uncommon presentation. Comprehensive neuroimaging and histopathological work-up are warranted for definitive diagnosis and management. To date, surgical resection remains the best curative treatment. However, leiomyosarcomas are usually friable and unencapsulated, which makes surgery challenging. Also, whether adjunctive chemotherapy will alter the long-term prognosis remains to be determined. Herein, we report the case of a middle-aged man who presented with proptosis and decreased vision, who was subsequently diagnosed with metastatic orbital leiomyosarcoma from a primary paratesticular tumour. We performed orbital enucleation with negative margins. The patient is currently under systemic pazopanib chemotherapy. LEARNING POINTS Orbital metastasis from paratesticular leiomyosarcoma is rarely encountered and shows aggressive behaviour.Clinical suspicion plays an essential role in diagnosing orbital leiomyosarcoma as this is an uncommon and atypical cause of proptosis and can be easily misdiagnosed by physicians.Curative surgical treatment should be considered due to the high recurrence rate.