How cancers metastasize remains poorly understood. The process begins when cancer cells break off from a tumor and invade blood and lymphatic vessels, the body’s alleyways. But studying invasion—typically...

Could the COVID-19 vaccine mess with your period? That’s what some vaccine recipients are saying, although there’s no confirmation that this is an actual side effect of the shot. Kathryn Clancy,...

More than a dozen children in New York City have been hospitalized with an unusual inflammatory syndrome possibility related to COVID-19. The syndrome, which doctors are still working to understand, has...