David, ThereseNarla, Swetha LakshmiSubramanyan, AnnapurneswariN., Kathiresan2025-06-282025-06-282025-06European Journal of Clinical and Experimental Medicine T. 23, z. 2 (2025), s. 524–5282544-1361https://repozytorium.ur.edu.pl/handle/item/11597Institutional Ethical Committee approval has been obtained (AMH-C-S-051/06-24).Introduction and aim. Chondrosarcomas are malignant cartilage-forming tumors, with secondary cases rarely arising from osteochondromas. This report presents a case of secondary chondrosarcoma developing from an undiagnosed pelvic osteo chondroma in a young female, emphasizing the importance of early detection and timely intervention. Description of the case. A 28-year-old woman with hip and back pain underwent magnetic resonance imaging, revealing a le sion in the left iliacus muscle with sacroiliac extension. Biopsy confirmed a chondroid neoplasm, and positron emission topog raphy-computed tomography showed minimal metabolic activity. Due to the extensive soft tissue component and recurrence risk, wide local excision was performed. Histology confirmed well-differentiated secondary chondrosarcoma, WHO grade 1 arising from an undiagnosed pre-existing osteochondroma. Conclusion. The described case highlights the critical role of radiological and histopathological evaluation, timely surgical in tervention, and multidisciplinary management for optimal patient outcomes.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/chondrosarcomailiac bonemalignant transformationosteochondromaarticle10.15584/ejcem.2025.2.25