Biological and clinical studies relevant to metastasis of breast cancer.

The progression of neoplastic epithelial proliferation in the breast does not inevitably lead to an infiltrating carcinoma. The carcinoma-in-situ which do metastasize apparently produce cells whose first moves through tissue are facilitated by lysing inert intercellular material (types I and IV collagen). Metastasis, defined as the capability of tumor cells to disseminate to distant sites in the body and set up secondary neoplasms, is a property separate and additional to tumorigenicity or local invasiveness. The driving engine of the metastatic process is identified as regulatory genomic disturbances in the population of cells within the tumor. Success or failure of secondary tumor growth in distant sites depends upon the outcome of interaction with local microenvironmental factors and systemic endocrine and immunological conditions.