Table 2. In vivo models of brain metastasis.

Brain metastasis method	Description	Disadvantages
Intracardiac or tail vein injection	Recapitulates the second half of the metastatic process Serial brain metastasis selection can increase the success rate of brain metastasis	Bypasses the first half of the metastatic process Animals may succumb to lung metastasis prior to brain metastasis formation
Intracarotid arterial injection	Recapitulates the second half of the metastatic process Reproducible, consistent, specific brain metastasis formation	Bypasses the first half of the metastatic process Technically challenging
Stereotactic intracerebral injection	Reproducible and consistent brain metastasis formation	Ignores all stages of the metastasis cascade except secondary organ outgrowth Bolus cancer cell injection to the brain parenchyma may not show the metastatic colonization of single or few cells