The Role of Cancer Stem Cells in the Organ Tropism of Breast Cancer Metastasis: A Mechanistic Balance between the “Seed” and the “Soil”?

Table 1

Interactions between primary cancer site and target organ based on metastatic efficiency indexes.

Primary cancer site	Target organ
	Kidney	Brain	Bone	Skeletal muscle	Skin	Heart	Thyroid	Adrenal
Bone	—	—	—	—	—	/	—	↑
Breast	—	—	↑	—	—	—	↑	↑
Cervix	—	—	—	—	↓	/	↑	↑
Colorectal	—	—	—	↓	—	—	—	↑
Esophagus	—	—	—	—	↓	/	↑	↑
Kidney	—	—	—	↓	—	—	↑	↑
Lung	—	—	—	/	/	—	—	↑
Lung(SCC)	—	—	—	/	/	/	—	↑
Osteosarcoma	↓	↓	—	↓	/	↓	—	↓
Ovary	↓	↓	—	/	—	—	↑	↑
Ovary*	—	↓	—	—	—	/	—	↑
Pancreas	—	—	—	—	—	—	—	↑
Prostate	—	—	↑	—	↓	↓	—	↑
Prostate*	—	↓	↑	/	↓	—	—	↑
Stomach	—	↓	—	↓	—	/	—	↑
Testis	—	—	—	↓	—	/	—	↑
Thyroid	—	—	—	—	—	/	—	↑
Urinary Bladder	—	↓	—	—	—	/	↑	↑
Uterus	—	—	—	—	↓	/	↑	↑

Adapted from Weiss (1992) [10].
↑ Friendly (Increased incidence) (MEI > 0.100).
↓ Hostile (Decreased incidence) (MEI < 0.009).
— Neutral (0.010 < MEI < 0.099).
/ Not reported.
SCC: small cell carcinoma.
*Duplicate sites due to different autopsy studies used.