During yearly blood check up, my 7 year old son cbc came back normal with few atypical lymphocytes found in blood film , is this normal ?

Very likely: Or he could have an unrecognized viral illness recently.

Probably fine: If the entire blood count is normal except for a "few atypical lymphocytes" then it most likely is a perfectly normal blood count. Check with your doctor and see his/her degree of concern and whether a repeat count is necessary sooner than a year Could be due to a recent viral exposure. the problem with doing blood tests as a screen in healthy people is that you find mild changes that mean 0

Atypical lymphocytes: The most common causes of atypical lymphocytes in the pediatric population are Epstein Barr virus, Pertussis and leukemia. There are many other causes as well, such as resolving viral infection. Usually this is not a finding of concern in otherwise healthy thriving children.