RBM10 truncation in astroblastoma in a patient with history of mandibular ameloblastoma: A case report

Astroblastoma is a rare glial neoplasm composed of cells that have broad processes oriented perpendicular to central vessels and often demonstrate vascular sclerosis. The WHO 2016 classification does not specify a grading system for astroblastoma, and categorizes them as well differentiated or malignant. These broad classification rubrics, however, do not accurately predict clinical outcome. Genetic profiling of astroblastoma has therefore been of particular interest in the recent years. These efforts, although in small number, have revealed heterogeneous molecular findings that may explain astroblastoma's unpredictable clinical outcome. Here, we report a case of recurrent astroblastoma in a 23-year-old female with a unique molecular characteristic. Our patient's tumor harbored an RNA-binding motif 10 (RBM10) truncation. RBM10 codes for a widely expressed RNA binding protein, and its mutation has been described in a variety of solid cancers. RBM10 is thought to be involved in stabilization of pro-apoptotic proteins in breast cancer, and its reduced protein expression is associated with advanced stages of lung adenocarcinoma. To our knowledge, this is the first report of astroblastoma harboring RBM10 truncation. Interestingly, our patient also has a history of mandibular ameloblastoma, but the link between these two rare tumors is unclear.