The mode of metastatic spread depends on anatomical, physiological and molecular and biolological peculiarities of the tumor.
The disease can spread (disseminate) both lymphatically and hematogenously. Most often tumorcells invade lymph vessels and spread to regional lymph nodes, primarily to the axillae.The lymph node involvement depends on the location of the primary tumor in the breast. Hematogenous dissemination leads to metastasis in the bone (40-75%), lung/pleura (2-15%) and liver (3-10%), but also in other organs, for example the brain or skin.
There are steadily more patients having breast cancer which is confined only to the breast at the time of diagnosis. More than 60% of all the patients have no lymph node metastasis, while approximately 25% have positive axillary lymph nodes. The remaining patients have a locally advanced disease, either in the form of a large tumor or growth into the skin and chest wall. A small portion of patients have spreading to other organs.
The number of patients having distant spread at the time of diagnosis has remained stable in the last years. It is important to distinguish between breast cancer patients with locoregional metastasis only (curable) and those with distant metastasis (incurable).