Significance of Histone H3.3 (G34W)-Mutant Protein in Pathological Diagnosis of Giant Cell Tumor of Bone

This study aimed to examine the expression of Histone H3.3 glycine 34 to tryptophan (G34W) mutant protein in Giant Cell Tumor of Bone (GCTB). This analytic observation research used a cross-sectional study design on 71 bone tumors. The cases involved 54 tissue samples diagnosed as GCBT. It was divided into GCTB primer (n=37), recurrent GCTB (n=5), GCTB with metastasis (n=9), and malignant GCTB (n=3). There were 17 samples mimics of GCTB also tested, including chondroblastoma (n=1), giant cell reparative granuloma (n=2), giant cell of tendon sheath (n=7), chondromyxoid fibroma (n=2), aneurysmal bone cyst (n=2), and giant cell-rich osteosarcoma (n=3). The Immunohistochemistry was used to evaluate the expression of G34W-mutated protein in these bone tumors. The representation H3.3 (G34W) was expressed in the nuclei of mononuclear stromal cells but not stained on osteoclast-like giant cells. This study was analyzed by the Chi-square test, Fisher's test, specificity test, and sensitivity test. We obtained p = 0.001 for Histone H3.3 (G34W) mutant expression in GCTB vs Non-GCTB. Statistically, there was no significant difference in the expression level of Histone H3.3 (G34W) in the GCTB and its variants p-value = 0.183. We also obtained that the specificity of Histone H3.3 expression on GCTB was 100% and the sensitivity of Histone H3.3 on GCTB was 77.8%. Histon H3.3 mutant as a mutated driver gene in an Indonesian GCTB can assist to diagnose GCTB and compare it from other bone tumors.