The singer reveals that she received her diagnosis in April and that the cancer is "in an early stage".
"Cancer sucks in all forms, but I cling to the word 'early'", says Jessie J.
Jessie J explains that she probably hasn't fully taken in the illness message due to too much lately, but that she wants to be open-hearted about her health condition with her fans.
"I know how much I've been helped by sharing and that I've received so much love and support. I'm like an open book and it's crushing that so many are forced to go through so much of this", says the British pop star.
The 37-year-old Jessie J broke through 15 years ago with songs like "Price tag", "Domino" and "Bang bang".