<prompt> A 5year-old child complains of pain and swelling of the right tibia. On laboratory evaluation he has elevated ESR and leucocytosis X-ray shows a tibial lesion. Which of the following is the best investigation which can help us clinch the diagnosis:Blood CSPus CSMRIBiopsy  <response>: Diagnostic is always Tissue Diagnosis -Tumors and infection can mimic each other clinically and radiologically, e.g. Osteosarcoma and Ewings sarcoma are two tumors that mimic osteomyelitis. Both have accompanying fever and increased local temperature. -Tumors and bone infections are usually metaphyseal and both need tissue diagnosis for differentiation. Thus, Culture is gold standard for infection -Histopathology is gold standard for tumors So rule is Culture all biopsies, biopsy all cultures. 