Chondroblastic osteosarcoma – Does this rare histological variant warrant a change in management?: A case report

Abstract

BackgroundOsteosarcoma is a primary bone malignancy occurring due to abnormal proliferation of bone forming mesenchymal cells. Chondroblastic Osteosarcoma is a rare variant of osteosarcoma which is associated with higher recurrence rate and metastatic potential. Case reportA 21 year old lady had complaints of pain in her left thigh for one year. On examination, a hard mass was palpable over the lateral aspect of the distal thigh. Radiographs revealed an ill-defined ‘fluffy’ osseous lesion involving the metaphyseal region of distal femur, and extending into the soft tissue. Computed tomography (CT) scan showed mixed lytic and blastic regions. CT guided core needle biopsy was performed. Histopathological examination showed a cellular lesion with chondroblastic differentiation and focal lace like osteoid formation. Immunohistochemistry confirmed the diagnosis of Chondroblastic Osteosarcoma. Two cycles of neoadjuvant chemotherapy was given, after which wide resection of the tumor and reconstruction of distal thigh, knee joint and proximal tibia with modular megaprosthesis was done. At 5 years follow up, she showed no evidence of recurrence, and was noted to have an excellent Musculoskeletal Tumor Society (MSTS) Score of 26. ConclusionChondroblastic Osteosarcoma is a rare variant of osteosarcoma which can be distinguished from classical osteosarcoma by histopathology. It is important to recognise this variant as it is associated with a higher recurrence rate and metastatic potential. Limb salvage surgery with megaprosthesis provided excellent functional outcome with no recurrence in our case.