YouTuber, science educator, and writer Hank Green announced on Friday that he has been diagnosed with Hodgkin lymphoma, a form of blood cancer that affects the lymph system.

Green, 43, announced his diagnosis in a YouTube video Friday morning. He said he had been diagnosed with the disease after noticing enlarged lymph nodes.

He explained the cancer is considered very treatable and that "the goal is cure."

He said he would begin chemotherapy soon. "I'm not really looking forward to it, but I'm looking forward to starting on the path," he said in the video.

Green has multiple risk factors for lymphoma, including medications, an autoimmune condition and having had mononucleosis in childhood, he said.

Green, who came to prominence through a collaborative YouTube channel with his brother John Green called "Vlogbrothers," said he wasn't yet sure how his diagnosis would affect his work.

"What am I gonna make? I don't know," he said. "I know that I'm gonna feel like garbage," he went on, referring to the effect of chemotherapy treatments. "It's gonna be really unpleasant."

He emphasized the importance of friendships in dealing with his diagnosis.

"All of the time that I have spent investing in friendships, and even when they have been hard, to try and keep them strong, and even when I have been busy, to try and spend time with them, has been joyful in the moment and wise in the long term," he said. "I've really needed friends in the last few weeks, and I've been very grateful to have them."

On Twitter, Green said he had started his first session of chemotherapy shortly after the video was released.

VidCon, an annual convention for YouTubers and other internet creators founded by John and Hank Green, announced that Hank Green would no longer be able to attend due to the diagnosis.

"We're sending all the love from the VidCon community & beyond," it wrote.

What is Hodgkin lymphoma?

Hodgkin lymphoma, sometimes called Hodgkin's disease, is a form of cancer that starts in the lymph system, according to the Centers for Disease Control and Prevention.

The lymph system plays a crucial role in the immune response, ferrying white blood cells that fight infection to different parts of the body.

The American Cancer Society estimates there will likely be around 8,830 new cases of Hodgkin lymphoma in 2023. The disease is the most common cancer diagnosed in adolescents between the ages of 15 and 19.

The five-year relative survival rate for all patients diagnosed with Hodgkin lymphoma is around 89%, according to the American Cancer Society.