Neck swellings >3 cm require acute referral even in an otherwise well child. Systemic illness, suspected malignancy, or suspected abscess are obviously grounds for urgent referral.
For harmless-looking cervical lymphadenopathy, the advice should be to return if still present in 7 days (or, obviously, if the child becomes systemically unwell). Continue reviewing every 1 – 2 weeks, and investigate further if not gone by 4 weeks.
Remember Kawasaki as a possible cause (only if >1 LN >1.5 cm). A much more mundane cause that I wouldn’t have thought of is headlice.
(From BMJ 2012;344:e3171 – 9th June)