Metastasis is the term used to describe how cancer spreads. When cancer cells move from the primary tumor in the breast and spread to other regions of the body, this is known as metastasis. Even after the initial diagnosis and treatment, Breast Cancer can return in another area of the body months or even years later. This is referred as as a distant or metastatic recurrence. Metastatic illness affects over 30% of women with early-stage Breast Cancer.