**3. Epidemology**

Population-based studies are generally considered more accurate and less biased than the more limited clinical (or) autopsy-based series [37]. The exact incidence of brain metastases is unknown. The epidemiological study is done by using the hospital records, tumor registers, and death certificates. Finally from this study, the incidence of brain metastases seems equal to the incidence of gliomas [38]. The survival rate by histology is summarized in **Figure 1**.
