Man diagnosed with aggressive blood cancer at 25 after mistaking blood in his stool for side effect of iron supplements

A man diagnosed with blood cancer at 25 that later progressed to stage 4 when doctors found a tumour in his brain said he feels like the “luckiest unlucky” person to now be in remission.

Marco Choi, 28, from Chelmsford in Essex, had been experiencing headaches, muscle aches and cold sweats from November 2023, but he put the symptoms down to working out at the gym.

He also experienced blood in his stool, but he mistook it as a side effect of taking iron supplements which can sometimes make your stool appear darker.

However, after he collapsed at work on December 13 2023, he was rushed to hospital and by January 2024, Marco was diagnosed with diffuse large B-cell lymphoma (DLBCL) – an aggressive type of blood cancer that affects white blood cells and is most commonly diagnosed in people in their 60s to 70s.

Six cycles of chemotherapy followed and Marco said it felt “amazing” to receive the “all-clear” by the end of July 2024. However, a month later, he had a seizure and doctors discovered a tumour in his brain.

He was diagnosed with secondary central nervous system (CNS) lymphoma, a “particularly aggressive and difficult-to-treat form of blood cancer where fewer than half of people survive”, according to Heidi Smith, nurse at Blood Cancer UK.

Marco had more chemotherapy, radiotherapy and an autologous stem cell harvest and transplant, which used his own stem cells to replace blood cells destroyed by high doses of chemotherapy.

By mid-June 2025, Marco said he was “very happy” to finish treatment and be told in August that same year he was in remission.

Recalling this moment, Marco told PA Real Life: “I felt amazing when I got told that.

“The first time I beat it, I thought it was all over and that was short-lived (but) this time, we laughed about it and said that it’s really over now.

“Two is more than enough and we don’t need a third time … It felt like I was getting closer to being myself again.”

In the months leading up to his cancer diagnosis, Marco said he was going to the gym “three to five times” a week and took supplements such as iron tablets and creatine.

But he said he would “go out and drink around three to five times a week” too.

“I was partying a lot and making the most of my younger years,” he said.

“I thought that I’ve got plenty of time, so I could still mess around or have fun and live life.”

So when he started experiencing symptoms of blood cancer – headaches, muscle ache, night sweats and blood in his stool – in November 2023, he did not think it was anything serious.

Then, on December 13, Marco collapsed at work.

“I was at the front of the (takeaway) shop and I was just taking an order on the phone,” he said.

“I just lost consciousness and fell down … then I remember waking up with one of the chefs patting me in the face.”

Marco was taken to Broomfield Hospital in Chelmsford, where doctors gave him a physical examination and realised he had internal bleeding that was causing blood in his stools which required 11 blood transfusions.

By the time he was discharged from hospital on December 23, doctors had discovered a mass in Marco’s chest, so he had CT and PET scans two weeks later.

On January 25 2024, Marco was diagnosed with diffuse large B-cell lymphoma.

Marco said: “When they told me I had cancer, it just felt surreal, like you’re in a dream.

“And it didn’t really hit me until I was on the bus back from the hospital and I had to tell my mum.

“She cried and that made me cry.

“We were just saying that we have got to keep going.”

From February 5, Marco said he had six rounds of “very intense” chemotherapy where he experienced gut issues, hair loss, difficulty sleeping, nausea and extreme breathlessness and wheezing that led to a hospital stay.

On the day Marco got the all-clear on July 29, he said he was “super happy” and his brother took him to Nobu – a Japanese restaurant in London – to celebrate.

But just as Marco said he was “trying to go back” to the “old me”, he had a seizure on August 28 while working out at the gym with a friend.

“The next thing I know, I wake up and I’m in the back of an ambulance with a massive headache,” Marco said.

Three days later, an MRI confirmed Marco had a tumour in his brain and his care was transferred to University College London Hospitals (UCLH).

He started chemotherapy again from September 6, then had an autologous stem cell harvest and later transplant – where your own stem cells are collected and stored, then given back to you later by transplant – and 20 sessions of radiotherapy.

Marco also had a brain biopsy on December 23 2024 after he had another seizure earlier that month, where he said a consultant remarked that he “might not see” 2025 because of his condition.

But he progressed and finished treatment on June 17 2025, and Marco said he “felt amazing” to be told just under two months later that he was in remission.

He is thankful for the support he has received throughout his cancer treatment from his mother Helen, 61, his older brother and sister, his friends and medical staff.

“My perspective really changed,” he said.

“And I wanted to repay all the kindness that I received … So that’s why I wanted to be an ambassador (for Blood Cancer UK).”

Nurse Heidi Smith told PA Real Life: “Marco’s story shows just how devastating and unpredictable blood cancer can be, even for someone in their 20s.

“It’s wonderful to hear that Marco is now back in remission after everything he’s been through, but sadly not everyone has the same outcome.

“His experience highlights just how urgently we need better treatment options for people whose blood cancer returns, particularly when it affects other areas of the body, like the brain.

“Through our £25 million Trial Treat Beat appeal, we’re determined to accelerate research and clinical trials to double survival chances for the deadliest blood cancers, giving more people like Marco the chance to survive and live their lives.”

Marco said he is sharing his story because when he was first handed a booklet about blood cancer, he noticed a “lack of diversity” in it.

“It didn’t really reflect me,” he said.

“I’m young, I’m active, I thought I was relatively healthy and I’m Asian, but I just saw white men who were older.

“Even the doctors made a joke that when they saw I was 26 on the file, they thought they read it wrong and I was 62.

“So I want to show that anyone can get (blood cancer).”

Marco is supporting Trial Treat Beat. To find out more about Blood Cancer UK’s plans to transform survival for people with some of the deadliest blood cancers, visit their website: bloodcancer.org.uk/about-us/our-campaigns/trial-treat-beat/.