Metastasis

Settlements of tumor] cells, which reach other tissue sites via blood, lymph and other pathways and develop their destructive function there.

The extremely complicated processes that take place in detail during metastasis (Greek: emigration) have been researched in recent decades, but have still not been fully clarified. Epitheliumien are known to be the uppermost cell layer - the covering tissue - of the skin and mucous membrane tissue. They sit on a very firm membrane, the so-called basement membrane, which is the first major obstacle for a cancer cell willing to emigrate.

To be able to move elsewhere, it must first break through the basement membrane. Then it must also penetrate the basal membrane of a vessel to enter its interior and be carried by the fluid in the vessel (blood or lymph). Later, it must adhere to a favorable site, again penetrate the vessel wall and the basement membrane, now to the outside, and - in order to settle and multiply at that site - form new blood vessels for its supply.

Most cancer cells die during this adventurous journey, but unfortunately some - about one in ten thousand - reach their deadly destination.

https://de.wikipedia.org/wiki/Metastase _{(Wikipedia CC-by-sa-3.0)}