Mum Gemma made the heart-breaking announcement on the Bradley Lowery's fight against neuroblastoma Facebook page.
Bradley has inspired people across Yorkshire to hold events and raise money to tackle the disease.
"This week has been crazy busy and extremely emotional," she wrote.
"As you aware Bradley has been in hospital and in excruciating pain, we have found it so difficult to see our baby like this. Bradley spent his birthday in hospital and asleep most of the day as he is really not well. Myself and his daddy have spent our time rubbing his legs and comforting him the best we can.
"On Thursday we were allowed to take Bradley home but unfortunately we have found another lump on his neck that is getting bigger very quickly and Bradley's consultant believes it is yet another tumour.
"Yesterday was Bradley's big birthday party and what an amazing party it was. Thank you everybody who was involved to make it so special, the fireworks at the end were out of this world, I've never seen a better display.
"So as you can see we have had a pretty hectic emotional heart breaking week. This leads me nicely into what I would like to say next. I appreciate everyone who does any fundraising no matter how little or big, no mater how much is raised for Bradley which will now go into his foundation to support other families, due to the fact there is no treatment options available for Bradley now.
"I would love to be able to thank you all individually but I've not got enough hours in the day, especially this week and Bradley can't do personal thank you's at the moment as he a very poorly little boy.
"Thank you to everyone for all your kind messages of support and wishing my superstar a happy birthday. "Thank you to my team I have helping me out going to events on behalf of Bradley and answering messages."