Watanabe S, Shimomura A, Kubo T, et al. - In this study, two patients with intrathoracic Synovial sarcoma (SS) harboring the BRAF V600E mutation were identified in the process of clinical sequencing. There were two patients who were the women aged 32 and 23 years, and both presented with SS18–SSX2-positive monophasic SS in the thoracic cavity. Via next generation sequencing, BRAF V600E mutations were detected and confirmed immunohistochemically by diffuse intense positivity to BRAF V600E mutation-specific antibodies. This research implies involvement of the mitogen-activated protein kinase pathway and the potential clinical implication of BRAF mutation screening in SS.