Metastasis

Noun

1. A change in nature, form, or quality.
2. The spread of something harmful to another location, such as the metastasis of a cancer.
3. A sudden or rapid transition from one point, topic or argument to another, often to evade an uncomfortable subject or to redirect the discussion.
4. 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.