Pseudocystic Osteosarcoma: A Potential Diagnostic Pitfall – Case Report

Introduction: Pseudocystic osteosarcoma (OS) is an uncommon variant of conventional OS. Clinical and radiological features are presented as benign process with a non-rapid growth rate. Treatment may be adversely affected by the delay in diagnosis or an appropriate invasive procedure. Case Presentation: We report a rare case of pseudocystic OS of the distal femur in a 6-year-old boy. Imaging findings revealed an osteolytic intra-compartmental tumor, that suggested either simple bone cyst or subacute osteomyelitis. The patient was first operated by lateral approach for curettage but histopathology showed conventional OS. Treatment had been managed by standard current chemotherapy and trans-epiphyseal intercalary resection through lateral approach. Reconstruction was done by a non-vascularized autograft within the induced membrane technique. At 3 years of follow-up, the patient remained disease-free with good anatomical and functional results. Conclusion: conventional OS can be presented in rare cases as a benign bone cyst tumor. This type of pseudocystic OS should be included in the differential diagnosis of bone cyst tumors and pseudo-tumors. Keywords: Osteosarcoma, pseudocystic, surgery, reconstruction.