Telangiectatic osteosarcoma in children and adolescents: Experience of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology scientific and clinical group on studying sarcomas of the locomotor system

Introduction. Telangiectatic osteosarcoma is a rare histological subtype of osteosarcoma, accounting for 2–12 % of all cases. Although telangiectatic osteosarcoma is characterized by unique morphological and radiological features, its diagnosis might be challenging due to its similarity to aneurysmal bone cysts and giant cell tumors. Aim. To evaluate oncologic outcomes in a large homogeneous series of children and adolescents with telangiectatic osteosarcoma. Materials and methods . The study included treatment-naive patients under the age of 18 with a diagnosis of telangiectatic osteosarcoma confirmed between January 1, 2012, and December 31, 2023, and prospectively registered at the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. All patients received MAP-based chemotherapy (according to the EURAMOS-1 protocol). Treatment outcomes were assessed using event-free survival and overall survival rates, calculated by the Kaplan–Meier method. Results . Among 368 primary osteosarcoma patients, the telangiectatic subtype was diagnosed in 40 cases (10.8 %). At initial diagnosis, 48.7 % of patients had pulmonary metastases, and pathological fractures were identified in 33.4 % of cases. Histological examination showed good response to preoperative chemotherapy in 76.3 % of patients. The median follow-up was 3.65 years. 5-year overall survival and event-free survival rates for all patients were 73.4 % and 57.3 %, respectively. Conclusion . Due to combination treatment including surgical tumor resection and neo- and adjuvant polychemotherapy, treatment outcomes for patients with telangiectatic osteosarcoma are similar to outcomes in patients with conventional osteosarcoma.