metastasize

Of a disease (especially cancer) or a tumour: to form a metastasis (“a secondary focus away from the primary site”) in (a body organ).

"I remember the first time he woke up throwing up, and my first thought wasn't, 'Oh he has the stomach flu,'" she [Rene McNall-Knapp] said. "It was, 'Oh, it's gone to his brain, and it's metastasized his brain, and he's throwing up because of that.'"

To disseminate or spread (something, often an undesirable thing), especially in a destructive manner.

In a broader sense, criticism as a form is in trouble. And celebrities like [Ariana] Grande, like [Michael] Che, like [Olivia] Munn, who swat at it to the delight of their fans, concerningly seem to metastasize the problem.

Of a disease (especially cancer) or a tumour: to undergo metastasis (“spreading from a primary site to one or more other sites in the body”).

On other screens are closeups of skin pores, before and after, details of regimes for everything, your hands, your neck, your thighs. Your elbows, especially your elbows: aging begins at the elbows and metastasizes.

Your lump could be a secondary cancer metastasized from the bowel. I had a patient like that not long ago.

Of a thing, often one which is undesirable: to disseminate or spread, especially in a destructive manner.

Late last month, a conservative website called The Federalist published an article advocating that healthy, young Americans deliberately infect themselves with Covid-19, […] If enough Americans expose themselves to the virus and become immune, the theory goes, the country would have a mobilized cadre of immune citizens. […] The article was widely discredited by public health experts and economists, as both logically dubious and ethically specious, but such thinking has already metastasized.