H3F3A mutations and the expression of
glycine 34 to
tryptophan (G34W) mutants in
giant cell tumors of bone (GCTBs) and other bone
tumors were detected to compare H3F3A mutation types and the expression of G34W-mutant
protein in order to provide a theoretical basis for using H3F3A mutations as a diagnostic and differential-diagnostic tool for GCTBs. A total of 366 bone
tumor cases were investigated. The cases involved 215 men and 151 women, whose median age was 29 years (3-84). The cases included GCTB (n=180), recurrent GCTB (n=19), GCTB with lung
metastasis (n=5), pediatric GCTB (n=15), primary malignant GCTB (n=5),
chondroblastoma (CB, n=61),
chondrosarcoma grade II (n=15), dedifferentiated
chondrosarcoma (n=17), chondromyxoid
fibroma (n=9), aneurysmal
bone cyst (n=9), nonossifying
fibroma (n=9),
osteosarcoma (n=16), and undifferentiated
sarcoma (n=6). Sanger
DNA sequencing analysis was used to detect H3F3A mutations. Immunohistochemistry was used to assess the expression of the G34W-mutated
protein in these bone
tumors.
DNA sequencing results revealed H3F3A mutations in 95.00% of GCTBs (171/180), including
glycine 34 to
tryptophan (G34W, 163/180, 90.56%),
glycine 34 to
leucine (G34L, 3/180, 1.67%),
glycine 34 to
valine (G34V, 3/180, 1.67%), and
glycine 34 to
arginine (G34R, 2/180, 1.11%). Recurrent GCTBs mostly had the H3F3A G34W mutation (18/19, 94.74%), and GCTBs with lung
metastasis all had the H3F3A G34W mutation (5/5, 100%). Pediatric GCTBs had a mutation rate of 93.33% (14/15), including one case with G34L. Four cases of primary malignant GCTB showed the H3F3A G34W mutation (4/5, 80.00%), and the classical GCTB component and malignant component showed consistent mutation types. Immunohistochemistry showed that GCTBs harboring G34W also expressed the
mutant protein in
tumor cell nuclei. Furthermore, one case of GCTB and one case of recurrent GCTB showed positive G34W immunostaining results despite being negative for the genetic mutation. Other bone
tumors all showed wild-type expression in both
DNA sequencing and immunohistochemistry. Our large-sample
DNA sequencing analysis detected four different forms of mutations in GCTBs, including three rare mutation forms. The most common mutation of H3F3A was G34W, which was in accordance with the expression of G34W in GCTBs detected by immunohistochemistry. Although
DNA sequencing analysis detected rare mutation types of H3F3A, false-negative results were also present due to the small number of cells in the samples. Detection of the most common (G34W)
mutant protein by immunohistochemistry was more convenient. Given the high prevalence of these driver mutations, the detection of H3F3A
mutant proteins can assist in the diagnosis of GCTB and its differential diagnosis from other bone
tumors.