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Editor,—Osteosarcoma is the most common primary malignant tumour of the bone. More than 90% of patients with this disease die with pulmonary metastases. Metastatic disease to the orbit from sarcomas is rare.1 An English language computer Medline search (from January 1966 to December 2000) for osteosarcoma metastatic to the orbit did not reveal any previous report. We describe perhaps the first case of osteosarcoma metastasising to the orbit.
An 8 year old boy was referred from a district hospital for a swelling over the proximal right leg of 5 months' duration. Lower extremity radiography showed a metaphyseal lesion in the proximal tibia with bone destruction and new bone formation. A clinical and radiological diagnosis of osteosarcoma was made. A plain chest radiograph did not reveal any abnormality. Histopathological examination of the tumour confirmed the diagnosis of osteosarcoma. An above knee amputation of the right leg was performed.
One month later, the child developed protrusion of the right eye (Fig1). An ophthalmic examination confirmed proptosis of the right eye. Vision, fundus, and eye movements were normal in both eyes. Ultrasound examination of the eye revealed a 12 mm × 18 mm lobulated, nodular, hypodense retrobulbar shadow on the temporal side, displacing the optic nerve medially. An area of necrosis was seen in the mass, but no calcification was present (Fig 2). Computed tomography of the orbit confirmed the findings of ultrasonography, demonstrating a soft tissue density mass in the right orbit displacing the eyeball. Fine needle aspiration cytology from the mass showed malignant spindle cells. A diagnosis of osteosarcoma with metastasis to right orbit was made. The patient was offered palliative chemotherapy but refused further treatment and was discharged from the hospital.
Osteosarcoma is the most common primary malignant tumour of bone. Most cases occur in children, adolescents, and young adults with a male predominance. The classic site of occurrence is the medulla of the metaphysis of the long bones, particularly the distal femur, proximal tibia, and proximal humerus. Metastases of osteosarcoma typically involve the lungs. Recent studies indicate, however, that the incidence of non-pulmonary metastases is increasing.2
Orbital metastases from malignant neoplasms are rare and can originate from anywhere in the body.3 In adults, the primary tumour is almost always a carcinoma, with breast and lung accounting for the vast majority of orbital metastases, followed in frequency by genitourinary and gastrointestinal primaries. In children with orbital metastases the primary tumours in descending order of frequency are neuroblastoma, Ewing's sarcoma, and Wilm's tumour.4 Jainet al 5 found leukaemia and neuroblastoma as the commonest tumours producing orbital metastases. The two populations studied in these reports differed geographically (United States and India respectively). These tumours tend to involve the orbits and spare the globes in contradistinction to metastatic disease in adults.4 Metastatic osteosarcoma to the eye is very rare. Newman and DiLoreto6 reported a single case metastatic to the eyelids. Spaulding and Woodfin7 and Lees8 have reported single cases of osteosarcoma metastatic to the choroid. The lung was not involved as a metastatic site in our patient. The spread of tumour to the orbit, sparing the lung, may have possibly been through the Batson's paravertebral system. Physicians should be aware that non-pulmonary metastases of osteogenic sarcoma may exist at unusual sites.