Chondroblastoma-like osteosarcoma of pelvis: A rare and aggressive subtype with diagnostic challenges and treatment implications

Osteosarcoma is a malignant bone tumor predominantly affecting adolescents and young adults, characterized by the production of osteoid matrix by malignant mesenchymal cells. Conventional osteosarcoma typically arises in the metaphysis of long bones and constitutes about 3 % of all primary bone tumors. Despite advancements in treatment, osteosarcoma remains challenging due to its aggressive nature and tendency for metastasis. Chondroblastoma-like osteosarcoma (CBLOS) is a rare variant that complicates diagnosis due to its resemblance to benign chondroblastoma, which is histologically and radiologically similar but typically benign. This case study highlights the diagnostic challenges and treatment implications of CBLOS, contributing to the understanding and management of this rare tumor A 17-year-old female presented with a three-month history of right hip and thigh pain, with no significant pre-existing conditions. Imaging revealed a lytic lesion in the right acetabulum with intense FDG uptake and MRI showing an aggressive mass with central cystic necrosis. Initial biopsies suggested chondroblastoma, but a third biopsy confirmed CBLOS, characterized by chondroblastic differentiation and a cellular stroma. The patient underwent neoadjuvant chemotherapy followed by extensive surgical resection, including type 2 + 3 pelvic resections and reconstruction using a tumor prosthesis. Postoperative recovery was smooth, and the patient is under regular follow-up for monitoring. CBLOS poses significant diagnostic challenges due to its resemblance to benign chondroblastoma and other bone tumors. Radiological features such as cortical destruction and mixed lytic-sclerotic patterns are crucial for differentiation. Histologically, CBLOS is distinguished by osteoid production, cytologic atypia, and aggressive cellular behavior. Radical surgical resection combined with neoadjuvant chemotherapy is the cornerstone of treatment, aiming for complete tumor removal while preserving function. Postoperative monitoring is essential to detect recurrence early. CBLOS is a rare and aggressive osteosarcoma variant requiring a comprehensive approach for accurate diagnosis and effective treatment. This case study underscores the importance of early detection, tailored treatment strategies, and the need for ongoing research to improve outcomes for patients with this challenging malignancy.