My son 15mnth went for ultrasound on lymph node he has for 2 months it measured about 8mm and he is having cbc blood work today could it be cancer?

Swollen lymph node: Swollen lymph glands can be caused by many things like infection ( viral , bacterial, fungi etc) , inflammation, malignancy etc. Viral/bacterial upper respiratory infection would be the most common cause of swollen lymph gland- especially in toddler. 8mm is small size of lymph gland. Don't worry.

I've never seen it: Swollen lymph nodes in infants and toddlers reflect reaction to infection, bug bites and dermatitis. I have never seen a kid with a swollen node in this age group have a cancer in 3 decades of work.I have read of some occurring in the teens or later years.