A 10-year-old boy who has jaw cancer and needs urgent surgery has vanished, a High Court judge has said.
Mr Justice Mostyn made a written order stating efforts should be made to find the boy, whom he said was Polish and could be in Poland with his parents.
He granted an application, made by an NHS trust, allowing doctors to perform surgery on the boy to remove a tumour.
A doctor said the child - who was not named - will die a "brutal and agonising death" without surgery.
Details of the hearing emerged in a ruling following hearings in the Family Division of the High Court in London.
'Frightened and fearful'
Mr Justice Mostyn said doctors believed the boy, who had lived in England with his parents for two years, was at risk of "serious harm" and the risk was growing each day.
He said there was evidence the boy had left his home with his mother two weeks ago, and that the boy's father had boarded a ferry bound for France in the past few days.
One doctor said the prospect of him growing up was "completely impossible" without surgery.
The paediatric oncologist said the boy's parents were "very frightened and fearful", worrying that he would be disfigured by surgery and preferring to treat him with "Chinese medicine".
Surgery could last as long as 12 hours and would require skin and bone from the boy's leg to rebuild his jaw bone, the judge said in his ruling.
It could result in "lameness", would leave the boy needing false teeth, and he could develop a "lopsided appearance", he added.
Mr Justice Mostyn stated: "I give full weight to the wishes of (the boy) as well as those of his parents.
"It is a strong thing for me, a stranger, to disagree with and override the wishes of (the boy) and his parents.
"But I have absolutely no doubt that (the boy) must be given the chance, a very good chance, of a long and fulfilling life rather than suffering, quite soon, a ghastly, agonising, death."
Mr Justice Mostyn said the Polish embassy in London was being alerted of the need to find the boy.
The judge referred to the boy and his parents by initials only and did not name the NHS trust.