Primary Osteogenic Sarcoma of Zygomatic Arch: A Case Report, With World Literature Review

Abstract

We report a rare case of osteogenic sarcoma of zygomatic arch presenting in a 20 year old male patient and a review of world literature on incidence and imaging. Craniofacial osteosarcomas are rare primary malignant bone tumours. This paper presents a case of osteogenic sarcoma of left zygomatic arch, showing erosion of middle aspect of left zygomatic arch with sun-ray spicules noted perpendicular to the cortex with multiple conglomerated new bone formation and associated soft tissue swelling extending inferiorly into the left infratemporal fossa and later diagnosed as osteosarcoma with chondroblastic differentiation. In head and neck, the most common sites of origin are the mandible, maxilla, nasal septum, hard palate and skull vault. More than 50% of craniofascial osteosarcomas arise in the jaw. Mandible is more commonly affected than maxilla. Zygomatic arch is a very rare site of involvement. Osteosarcoma should be considered in the differential diagnosis of lytic lesions with associated soft tissue swelling of zygomatic arch. Only four cases of primary osteogenic sarcoma of zygomatic arch have been reported in the English-language literature. KEYWORDS: Primary Osteogenic sarcoma, zygomatic arch, computed tomography. CASE REPORT:A 20 year old man sustained trivial trauma in the left malar region thereafter he noticed some swelling in the same region about 2 months back. It was painless swelling and increased in size within 2 months. On local examination, a 7x 6 cm hard, non-tender, non-mobile swelling was present in the left malar region extending upto the left preauricular region. Cranial nerve examination was normal with no ophthalmoplegia or visual changes. There was no clinical evidence of intraoribital or intracranial extension.Computed tomography scan (CT Scan) revealed osteolytic areas with erosion of middle part of left zygomatic arch on its medial and lateral aspects with subtle cortical discontinuity at places in this part of zygomatic arch. Wide zone of transition is noted. Areas of new bone formation representing the osteoid matrix, with a large soft tissue component surrounding the left zygomatic arch and extending inferiorly into left infratemporal fossa were noted. The medullary cavity of this part of the zygomatic bone showed soft tissue density within, suggestive of marrow infiltration ( Figure 1 and Figure 2). Periosteal reaction is not appreciated. The soft tissue swelling was seen abutting the superficial lobe of left parotid gland.Osteogenic sarcoma and Ewing's sarcoma were considered in differential diagnosis considering the age, presentation and imaging features. Later on CT Scan of Chest was done to rule out any lung metastasis. The study was negative. True-cut biopsy of the lesion revealed features of osteosarcoma with predominant chondroblastic differentiation. Chest radiograph, hemogram and liver function tests were normal. The patient was taken up for surgery and a radical excision of tumour along with left zygomatic arch with lateral tarsorraphy done.