Metastatic Organotropism: An Intrinsic Property of Breast Cancer Molecular Subtypes

It has long been known that some cancers have the propensity to metastasize to certain organs thus creating a nonrandom distribution of sites for distant relapse, a phenomenon known as "metastatic organotropism." Some of these examples include ovary primary to abdominal cavity, prostate primary to bone, and pancreas primary to liver. In contrast, other tumor types, such as mammary and renal cell carcinoma, can relapse in multiple organs although approximately half of advanced breast cancers metastasize to bone. On the other hand gene expression profiling studies have identified various breast cancer classes with prognostic significance. Recent studies have revealed that breast cancer subtypes differ not only in primary tumor characteristics but also in their metastatic behavior. In particular, the luminal tumors are remarkable for their significant bone-seeking phenotype; the HER2 subtype demonstrates a significant liver-homing characteristic; whereas so-called triple-negative breast cancers predispose to lung metastases. These findings suggest that this knowledge could potentially be utilized in the development of effective disease surveillance strategies in the pursuit of precision medicine, thus necessitating further investigation.