Abstract: Objective To investigate the association of mutations in the EXT and FGFR3 genes with osteochondroma of the condyle and to provide a basis for clinical treatment of condylarosteochondroma. Methods Clinical manifestation and imaging features of patients with condylar osteochondromaadmitted in our hospital from January 2017 to June 2021were analyzed. Peripheral blood was used for gene whole-exome detection, and the expression of FGFR3 and EXT1 proteins in the tissues was detected by immunohistochemical methods. Results There were 10 cases of isolation condylar osteochondroma. The male-to-female ratio was 1∶1.5; the mean age was 37.1 years, and the ratio between left side and right sidewas 9∶1. Three patients who underwent whole-exome test all had FGFR3 gene mutation; two of them had common site mutations. Two cases had EXT1 gene mutations whichwere located at the same site. Immunohistochemical staining showed positive EXT1 expression in 8 of the 10 condylar osteochondromas and FGFR3 expression was also positive in 1 case. Conclusion The condylar osteochondroma is not only related to EXT1 gene mutations but may also relate to FGFR3 gene mutations. However, results of whole-exome detection and immunohistochemical staining are inconsistent, and specifically related mechanisms need to be further studied and confirmed.

Key words: EXT gene, FGFR3 gene, condylar osteochondroma, condylar hyperplasia