Tehran University of Medical Sciences Journal of Orthopedic and Spine Trauma 2538-2330 12 2 2026 05 18 107 11 EN Sadegh Saberi Associate Professor, Department of Orthopedic Surgery, Joint Reconstruction Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran Aysan Valinejad-Qanati Medical Student, Center for Orthopedic Trans-Disciplinary Applied Research, Tehran University of Medical Sciences, Tehran, Iran Seyyed Saeed Khabiri Assistant Professor, Department of Orthopedic Surgery, Joint Reconstruction Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 2025 08 23 2026 05 18 This case-based expert review from ORTHOBIT 2025 Congress (Tehran, Iran) highlights the practical challenge of distinguishing between enchondroma/atypical cartilaginous tumor (ACT) (low-grade) and higher-grade chondrosarcoma (CS). A 57-year-old woman presented with 4 months of shoulder pain. Magnetic resonance imaging (MRI) revealed a proximal humeral metaphyseal intramedullary cartilaginous lesion with a focal cortical breach and a small extraosseous component. The core needle biopsy (CNB) suggested enchondroma, and the patient underwent extended curettage, cementation, and plate fixation. Final pathology upgraded the lesion to central CS, grade 2, prompting resection and reconstruction using a proximal humeral megaprosthesis. At 3 years, she was pain-free, recurrence-free, The Musculoskeletal Tumor Society Score (MSTS) 26/30, with moderate range of motion (ROM) limitation, and radiographic superior prosthetic migration without major complications. This case emphasizes the importance of radiology-pathology correlation and planning for possible diagnostic upgrading in borderline cartilaginous tumors. https://jost.tums.ac.ir/index.php/jost/article/view/704 https://jost.tums.ac.ir/index.php/jost/article/download/704/472