What's the noun for metastatize? Here's the word you're looking for.
metastasis
(medicine) The transference of a bodily function or disease to another part of the body, specifically the development of a secondary area of disease remote from the original site, as with some cancers.
(figuratively) The spread of a harmful event to another location, like the metastasis of a cancer.
(rhetoric) Denying adversaries' arguments and turning the arguments back on them.