Factors
Not every primary tumor has the same potential to form metastases. On the one hand, this depends on the type of tumor and the characteristics of the tumor cells, but on the other hand, it also depends on the body of the affected patient, in particular his or her immune system. A prerequisite for metastasis is always the so-called “invasiveness” of the primary tumor, i.e. the ability to infiltrate surrounding blood and lymphatic pathways.
Tumors, which lack the property of invasion are benign by definition, if they have this property they are called malignant. In addition to the invasion of vascular tracts, tumor cells must be able to detach themselves from the original primary tumor, this they do by means of a reduced number of adhesion molecules on their cell membranes, they must survive the attacks of the immune system in the blood or be considered non-pathogenic (disease-causing) for it and they must be able to attach themselves to the new tissue, this happens by means of certain adhesive proteins, “integrins” and finally be able to adapt to the conditions there. This is opposed by the body’s natural defense system.
Depending on the type of scattering tumor cells, they are recognized by the immune system or not. If a tumor cell possesses the above mentioned properties and enters vascular tracts, it is difficult for our own defense to distinguish these cells from good endogenous cells, since the tumor cells are derived from them.Furthermore, tumor cells that divide quickly carry a special surface protein (CD 44) that signals to the body that this is a cell that legitimately changes places and does not erroneously multiply so quickly. Nevertheless, our immune system also recognizes metastatic tumor cells and eliminates them. If our immune system is now weakened and has less capacity to deal with these cells, it is of course easy for them to reach new hosts through blood and lymph channels.
