The unfortunate child has disseminated (bilateral nodes AND
posterior triangles) disease, and the mainstay of treatment will be
ablative doses of I131, with T4 and TSH suppression.
But first you must remove all tissue that will take up I131, as
safely as you can, incurring as little morbidity. This implies a
total thyroidectomy, and node "picking".
[I wonder whether a Surgeon is going to stick their neck out by
suggesting bilateral radical block dissections, and clearance of the
posterior triangles? Rather like Vesalius would have imagined.]