Often during the development of earlier stages of the tumor, or perhaps by the
time the tumor has broken through the basement membrane (as pictured above),
angiogenesis takes place. Angiogenesis is the recruitment of blood vessels from
the network of neighboring vessels. (A similar growth of lymph vessels may also
take place.)
Without blood and the nutrients it carries, a tumor would be unable to continue
growing. With the new blood supply, however, the growth of the tumor
accelerates; it soon contains one billion cells and, now the size of a small
grape, is large enough to be detected as a lump.
