Blake Lively Apologizes for "Silly" Joke About Kate Middleton ...

Now, it's clear that Kate was absent from the public spotlight to focus on her health and family. As the 42-year-old explained in a March 22 video on her social media accounts, "It has taken me time to recover from major surgery in order to start my treatment. But, most importantly, it has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be OK."

Kate—who did not disclose the specific type of cancer her doctors found—also noted that the past few months have been "incredibly tough."

"In January, I underwent major abdominal surgery in London and at the time, it was thought that my condition was non-cancerous," she shared. "The surgery was successful. However, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the stages of that treatment."