Extraskeletal mesenchymal chondrosarcoma is a rare type of tumor an highly aggressive, an orbital localization is extremely uncommon and rare. We report a rare case of 30-year-old woman who was diagnosed with this type of tumor. 

A 30-year-old woman reports that approximately 6 months ago she began to experience sudden and progressive vertical binocular diplopia, associated with ocular proptosis and chemosis in the right eye. Absence of systemic signs. On examination, ocular hypertrophy was evident on the right, vertical gaze deviation, limitation of the infectious-medial gaze, associated with proptosis and enophthalmos. Visual acuity was preserved in both eyes. No alterations were present in the left eye. A cranial magnetic resonance imaging  (MRI) scan showed an expansive orbital lesion on the right infiltrating the inferior rectus muscle belly, with a hypointense signal on T2, restricted diffusion and heterogeneous contrast enhancement. Screened for tuberculosis and IgG4 disease negative. An incisional biopsy of the inferior rectus muscle was performed, with histopathological and immunohistochemical results of mesenchymal chondrosarcoma. No meningeal involvement was evidenced on neuraxial MRI and negative tomographic screening for secondary implants. The patient began neoadjuvant treatment with the chemotherapy regimen vincristine, doxorubicin, cyclophosphamide (VAC), ifosfamide and etoposide (IE), with a proposal for exenteration after neoadjuvant therapy. 

Our case indicates a mesenchymal chondrosarcoma of the orbit. A rare and aggressive type of tumor, which typically exerts a compressive effect on the ocular globe causing the ocular symptoms. The mainstay of treatment is complete removal of the tumor is and may be associated with neoadjuvant therapy.