S26 Journal of the College of Physicians and Surgeons Pakistan 2017, Vol. 27 (Special Supplement 1 of Case Reports): S26-S27 INTRODUCTION Osteosarcoma (OS) is a rare but highly malignant bone tumour. Excluding multiple myeloma, it is the most frequent primary malignant lesion of the bone in patients who are below 40 years of age. OS account for about 20% of all the sarcomas and about 4 - 6% occur in the maxillofacial region. 1 The characteristic clinical presentation of OS of the long bones is bone pain. In the jaw lesions, pain is not a prominent feature; swelling and paresthesias of the involved region are the commonest presenting complaints. 1,2 Although clinical presentation is typical, histopathological and radiographic appearances of OS vary. Radiographic features depend on the inter- relationship between the destruction of the pre-existent cortical or medullary bone, calcification or new bone production, and periosteal new bone formation. 3 CASE REPORT A 30-year male presented with the chief complaint of painful swelling in the right back region of his lower jaw for 6 months. Initially, the swelling was small and asymptomatic but from last 2 months, it started increasing in size and pain started from last few days. The past medical history and family history were not relevant to the present swelling. Extra-oral examination revealed a noticeable facial asymmetry on the right side of the face. Intra-oral examination revealed a large swelling extending from tooth ≠44 to the ramus of the mandible, measuring about 5 x 4 cm antero-posteriorly and medio-distally. On palpation, it was hard and fixed to the underlying structure. The overlying mucosa varied in color from yellowish to reddish (Figure 1a). The cervical lymph nodes were hard and painful on palpation. Panoramic radiograph revealed a mixed rediopaque - radiolucent lesion extending from tooth ≠33 to ≠44 with irregular attenuation of lamina dura, irregular areas of osteolysis and localised widening of periodontal ligament (Figure 1b). On the basis of clinical and radiographic features, a provisional diagnosis of OS with the differential diagnosis of osteoblastoma was given. Patient was referred to the Department of Oral and Maxillofacial Surgery. An incisional biopsy was performed and the tissue was sent to the Department of Oral and Maxillofacial Pathology for the microscopic evaluation. Histopathological examination revealed malignant osteoblasts and neoplastic bone formation in the connective tissue stroma (Figure 2a). The malignant osteoblasts were pleomorphic, hyperchromatic, and had few mitotic figures (Figure 2b). The overlying epithelium was normal stratified squamous epithelium which was hyperplastic at places (Figure 2c). The histopathological features confirmed the diagnosis of osteoblastic OS. After histopathological confirmation, other investigations like chest radiograph, lung and body scans were performed which were negative for other primary as well as metastatic lesions. Radical hemi-mandibulectomy was performed (Figure 2d) with a supportive chemotherapy. Reconstruction of the defect was performed using supraclavicular flap and reconstruction plates. The resected margins were negative for tumor and 6 months follow-up period was uneventful. CASE REPORT Osteogenic Sarcoma of Mandible Manas Bajpai, Nilesh Pardhe, Betina Chandolia and Manika Arora ABSTRACT Osteosarcoma (OS) is a malignant neoplasm characterised by the formation of osteoid matrix by neoplastic cells. It is the most common primary malignant bone tumor accounting for 20% of all sarcomas, although its occurrence in the jaw is rare. It shows typical clinical behaviour but varied radiological and histopathological features. It presents various histological aspects. We report a case of 30-year male presented with a painful swelling of mandible, diagnosed as OS after histopathological evaluation. Key Words: Osteosarcoma. Osteoblasts. Mandible. Department of Oral and Maxillofacial Pathology, NIMS Dental College, Jaipur, India. Correspondence: Dr. Manas Bajpai, Assistant Professor, Department of Oral and Maxillofacial Pathology, NIMS Dental College, Jaipur, India. E-mail: dr.manasbajpai@gmail.com Received: March 16, 2016; Accepted: August 17, 2016. Figure 1: (a) Intra-oral view of the lesion. (b) OPG reveals a mixed radiopaque - radiolucent lesion of anterior mandible