Atypical presentation of osteosarcoma: A case report

We present a 4-year-old male who presented with right arm mass and deformity following a fall onto his forearm. On imaging, the entire right humerus was involved by an aggressive, infiltrating process with associated extraosseous masses. This was proven to be osteosarcoma (OS) on biopsy. This is a rare diagnosis in this age group. The imaging features are also non-characteristic for OS wherein the entire length of the long bone is involved. OS should be included in the differential for aggressive bone tumors in the pediatric age group regardless of the known bimodal age distribution.