In Sam Neill's new memoir, the Jurassic Park star revealed he had been diagnosed with stage 3 angioimmunoblastic T-cell lymphoma.

But before receiving that diagnosis, Neill's doctor blamed the 75-year-old's swollen glands on a case of "undetected COVID," he Writes in Did I Ever Tell You This?

"At the beginning of March 2022 I flew to Los Angeles on matters Jurassic," Neill explains of when his health journey began. "About eight of the cast had an entire three-day weekend doing interviews, photo spreads for Vanity Fair and all of that stuff — publicity. It was a blast to catch up with my idiot friends and goof around as per. I noticed the glands seemed to be up in my neck region, but gave it very little thought. My agent had to kill a few photographs because my neck looked lumpy. Alan Grant doesn't have a lumpy neck, it seems."

Neill consulted his doctor in Sydney about the issue.

"I said, These lumps don't seem to be going down, and I don't know why," Neill writes. "He assured me that my lumpy glands were due to undetected COVID, and they'd be hanging around for a little while. I went back a week later when they were even bigger. This time he sent me in to hospital for some tests."

Neill went for a PET scan that led to his blood cancer diagnosis. "Within a few days I was lying on a hospital bed having all kinds of chemicals draining into my system, killing everything aboard," the New Zealander writes. "For therapeutic reasons. To be cured of a thing I didn't know I had just a few days ago. Yep, suddenly things are different — this is some serious s---."

Neill embarked on four rounds of chemotherapy and lost his hair not long after completing the first.

"After my first chemo, it took only a little over two weeks for the hair to disappear completely from the top of my head," the actor writes. "My brother was unkind enough to say, as we FaceTimed, Black men look cool bald, but white men look like some giant's thumb. I am no exception. I look like a boiled egg that's been sitting around in the pot long after the water has dried up. Someone has peeled that egg, but not very well."

Neill noticed his hair from his beard starting to fall out, too, so he shaved it off. "I've had a beard for quite some time, and this has meant I haven't seen my own face for many years," he writes. "Fifteen years, I'm thinking. And here was my face, now entirely unadorned. This was no small shock. Time has not been kind to it in the meantime. I'm not just wrinkled in the space where there formerly resided a beard, I am positively wizened. Three or four strokes of my trimmer and I had aged twenty years."

A second PET scan confirmed the chemo had been working, but a third PET scan showed the tumors had returned, so Neill and his doctors abandoned the first chemo for a different drug.

Neill writes that that fourth round of chemo "got a bit bumpy." Still, he attempted to do voiceover work during that time.

"I started recording a major series, 10 hourly parts, and my voice simply ran out on episode two," Neill writes. "This was something of a psychological blow. I've never not finished a day's work before, never. Rightly or wrongly, it made me feel enfeebled."

Neill checked in with his doctor, who told him his throat was ulcerated. Tests showed Neill had a low T-cell count, so he started taking daily injections "of who knows what," he writes, that caused Neill to have night sweats.

But he stayed positive through the treatment — and dancing helped. "I am still optimistic, and this optimism is maximised when I do a bit of a dance around the place," Neill writes. "To the right music, of course."

Neill's fourth PET scan determined his cancer was in full metabolic remission. "Now I'm a living man, with every intent of going on living and living and living," he writes.

On Instagram Saturday, Neill gave an update that he's been in remission for eight months now, "which feels really good," he captioned a selfie video. "And I'm alive and kicking and I'm going to work. I'm very happy to be going back to work."

The two-time Emmy nominee dedicated his memoir to his doctor, Orly Lavee, and "all my friends at St Vincent's."

"I wouldn't have started the book without you," he writes. "And I would certainly never have finished it."

Did I Ever Tell You This? is out now.