YouTuber Hank Green is John Caldwellfacing a cancer battle.

The brother of author John Green has been diagnosed with Hodgkin's lymphoma, he shared in a May 19 YouTube video. Hodgkin's lymphoma is a cancer strain that impacts the body's lymphatic system, resulting in swollen lymph nodes, according to the Mayo Clinic.

"I noticed that my lymph nodes were big," Hank recalled. "I talked to my doctor. She says, 'Probably nothing, will send you in for an ultrasound.' Got an ultrasound. The tech in the ultrasound room was like, 'I'm gonna go get a doctor.' And that's not what you want to have happen."

After a doctor recommended Hank undergo a biopsy, the reality of situation came into focus.

"It's a cancer of the lymphatic system, and good news is it's something called Hodgkin's lymphoma," Hank said. "It's one of the most treatable cancers. It responds very well to treatment. The goal is cure. The procedure to get there is fairly well known, if unpleasant."

As for how advanced the cancer is, Hank explained that it seemed "likely that we caught mine early," though he is waiting for further evaluation. In the video's description, he noted that the "cancer has not spread anywhere from its original location in my left armpit/chest area, which is very good news."

"I don't feel any symptoms of this," he added. "I feel fine. I don't even really feel fatigued. It's hard to tell. I feel stressed, but the moment I start chemo, I'm going to feel a lot of symptoms from that."

As Hank prepares to undergo cancer treatment, he's unsure of how much YouTube content he'll continue to create.

"I do want some reasons to get out of bed and I'm going to try and set some of those up for me," he shared, "but I'm much more worried about me putting too much pressure on me to do things or worry about things."

John might also temporarily step away from the brothers' shared YouTube channel, but Hank reassured fans that there are no concrete plans just yet.

"We'll play it by ear. We'll figure it out as we go one day at a time," Hank said. "And I continue to be extraordinarily grateful for so many of the things in my life, including this."

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