Kate Middleton ‘shock' cancer knowledge was ‘very tight'

Kate Middleton’s cancer information was released to very close people, says an insider,

The Princess of Wales ‘circle of information ion’ was very tight as to maintain privacy.

"It was a heck of a shock," the source tells PEOPLE before adding: "The circle of knowledge was very tight. "

This comes almost a week after Kate announced her cancer diagnosis .

In a heartbreaking video on Instagram, the mother-of-three revealed: "I am well and getting stronger every day by focusing on the things that will help me heal; in my mind, body and spirits."

"At this time, I am also thinking of all those whose lives have been affected by cancer. For everyone facing this disease, in whatever form, please do not lose faith or hope," she concluded. "You are not alone."