Low grade central osteosarcoma (LGCO) are rare intramedullary bone tumours of adolescents and young adults with an excellent prognosis. They have a predilection for long bones around the knee joint, but cases have been reported in long bones of arm, tarsals and flat bones of jaw, ribs and scapula as well. Their transformation to high grade sarcomas are rarely seen. We report a case of an 16 years female who presented with complaints of progressive pain in the lower thigh 2 years back. Her x-ray suggested a simple bone cyst in distal femur, following which wide excision of the cyst was done. Histopathology however showed features of LGCO. The patient was apparently alright in the follow up period until 9 months ago when the patient had a recurrence of swelling accompanied with pain at the same site leading to difficulty in walking. This time her X-ray showed neoplastic changes after which the tumor was excised. On microscopy, areas of high grade sarcoma with soft tissue extension were seen predominantly. This case is being reported to make the clinicians and diagnosticians aware of the rare but highly significant implication of transformation of LGCO to high grade tumors as it carries a guarded prognosis and calls for a different treatment strategy compared to conventional LGCO.
Key Messages: Low grade central osteosarcoma (LGCO) are rare intramedullary bone tumors seen in adolescents and young adults. It bears an excellent prognosis. We present a case report on LGCO showing transformation to a high grade sarcoma that radically changes its prognosis as well as calls for a different treatment strategy.
Central osteosarcomas, Dedifferentiated osteosarcomas, Intramedullary osteosarcomas.