Surface osteosarcoma, also known as paraosteal or juxta-cortical, is a specific form of this type of bone tumor that originates on the external surface of the bone, without involvement of the bone marrow. In this type of lesion, the tumor growth zone is visible on the bone surface, indicating a more immature region of the bone. Surface osteosarcoma can present two distinct histological representations:

– Low Grade: Characterized by the almost complete absence of atypical mitoses and morphologically similar to mature bone. The diagnosis is usually confirmed through clinical evaluation and imaging tests.

– High Grade: It has similar clinical characteristics, but exhibits atypia and a polymorphic pattern of immature neoplasia.

Clinically, surface osteosarcoma generally presents a slow evolution and tends to occur in individuals in the third and fourth decade of life. The most common locations include the posterior and distal metaphyseal region of the femur, popliteal cavus, proximal humerus, and distal radius.

Radiologically, this form of osteosarcoma is characterized by a dense lesion of tumoral bone neoformation, with its base in continuity with the cortex of the affected bone. The surface of the lesion may have a cartilaginous layer, representing the most immature area of ​​the tumor.

One of the main differential diagnoses is myositis ossificans, which exhibits an immature central area in the lesion, while the periphery is more mature and calcified.

Treatment of low-grade surface osteosarcoma generally involves oncological resection of the lesion, which may be partial, parietal or segmental, followed by reconstruction with an autologous bone graft or endoprosthesis. High-grade osteosarcoma is treated in a similar way to central osteosarcoma, with protocols that include chemotherapy, surgery and then adjuvant chemotherapy.

In summary, understanding the clinical, diagnostic and therapeutic aspects of surface osteosarcoma is crucial to ensure an effective and personalized approach for each patient, always aiming to achieve the best clinical results and good quality of life.