Hi, my son is 3 years old. When he was about 5 months old I notice something on his neck. Looked like an enlarged lymph node, right in the middle of the neck, left side. We did ultra sound when he was a year old. The doctor told us a lymph node, nothing to worry about. We did another ultrasound when he was 2 and a half. the same thing "lymph node and it is getting smaller". About a month ago I noticed there was already two "little balls" on his neck. We went to the doctor, she found the third one. so now it looks and feels like bunch of grapes. What specialist should we go to? Can it be something serious?