Abstract

Background: Giant cell tumor of bone is a bone lesion with diverse histological features, therefore diagnosis often requires a combination of clinical findings, imaging, and histopathology. Recently, the H3F3A gene mutation has been identified as a characteristic molecular marker of this tumor. Additionally, the immunohistochemical antibody against H3.3 G34W has been applied in practice to support diagnosis. Therefore, we conducted this study to investigate the histological features of giant cell tumor of bone and the expression rate of the H3.3 G34W marker. Objectives: To investigate the immunohistochemical expression of the H3.3 G34W marker in giant cell tumor of bone in relation to age, location, gender, and histological features. Materials and Methods: A descriptive cross-sectional study was conducted. The study included 91 cases diagnosed with giant cell tumor of bone by HE staining and imaging from June 2024 to December 2025. The study cases were examined under microscopy, with representative regions selected for TMA (Tissue Microarray) construction and immunohistochemical staining for the H3.3 G34W marker. Results: H3.3 G34W expression was independent of clinical features including age, gender, and tumor location. Conclusion: The high expression rate of H3.3 G34W in giant cell tumor of bone demonstrates its important role and practical utility, especially in locations and age groups where giant cell tumor of bone is less commonly seen.