Jane Fonda has been diagnosed with non-Hodgkin's lymphoma and is undergoing chemotherapy, the actor and activist announced via Instagram on Friday.
The 84-year-old Oscar-winner also used the post to express her optimism.
"This is a very treatable cancer. Eighty per cent of people survive, so I feel very lucky," Fonda wrote.
"I'm also lucky because I have health insurance and access to the best doctors and treatments. I realize, and it's painful, that I am privileged in this."
Fonda continued that she has been going through chemotherapy for six months now and has been handling the treatments well, adding she will not let this interfere with her climate activism.
Non-Hodgkin lymphoma is a cancer that begins in the white blood cells and affects parts of the body's immune system.
Fonda describes diagnosis as 'a teacher'
She described her cancer as "a teacher" and said that she is paying attention to the lessons it holds for her.
"One thing it's shown me already is the importance of community," said Fonda. "Of growing and deepening one's community so that we are not alone. And the cancer, along with my age … definitely teaches the importance of adapting to new realities."
Fonda's latest film Moving On, starring her former Grace and Frankie co-star Lily Tomlin, is making its world premiere at the Toronto International Film Festival this year. Fonda is not expected to attend the red carpet.