Giant Cell Tumor of the Bone in Young Patients

Inclusion Criteria: 1. Male and female patients under 15 years old treated at Rizzoli Institute from 01 January 1982 to 31 December 2018. 2. Diagnosis of giant cell tumor of bone, aneurysmatic bone cysts with solid features and giant cell reparative granuloma. 3. Histological slides/formalin-fixed paraffin-embedded tissue tumor blocks from archive available to perform the histology analysis 4. Written informed consent prior to any study-specific analysis and/or data collection Exclusion Criteria: 1. Patients with histological diagnosis different from diagnosis of giant cell tumor, aneurysmatic bone cysts with solid features, and giant cell reparative granuloma. 2. Patients with no available material for additional immunohistochemical and molecular analysis