Table 1.

Risk factors, identification, and chances of BM in BC patients.

Risk Factors	Identification	Brain Metastasis Risk	References
Lymph nodes	Histopathology	Positive lymphnodes-4, HR = 2.5, p = 0.029	[23]
Tumor grade	Histopathology	The grade of the tumor is 3; Rate is 7.9% after 10-years completion of follow-up	[24]
Tumor size	Histopathology	The size of the tumor is 2 cm, after 10 years with a 7% rate. Size of tumor greater than 2 cm have a high risk of BM	[25]
Luminal A and B subtypes	Molecular biology	Over-expresses of epidermal growth factor of a human determined as HER-2	[26]
AlphaB-crystallin (CRYAB)	Genetic biomarker	Occurrence of BM	[27]
Phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK/ERK)	Molecular biomarker	Overexpression of HER 3 receptor MAPK signaling pathway preferentially activated in the BM of cancer patients	[23]
VEGF and CXCR-4	Molecular biomarker	Disrupt the BBB with migration in the parenchyma region	[28]
A2,6-sialyltransferase	Genetic driver	Cancer cell extravasations in the course of the BBB	[29]
Adjuvant trastuzumab trials	Targeted therapy for HER2-positive	BM risk was increased with a range of 1.32 to 1.9	[30]