Question of sed rates in 3 year old

HI,
My son has had fevers (104-105) of unknown origin for many months (only motrin worked on them), weight loss and anorexia during the fevers and the last fever he has drenching night sweats.
His first sed rate was 23 (no fever at time of blood draw)
second 114 (quite sick with 104-105 fevers for many, many days)
was hospitalized C-reactive in hospital was >100
third sed rate in hospital was 83
Discharged- no answers- lupus, arthritis, TB, blood cultures, etc. everything negative.  

two weeks later sed rate is 34 (no fever at time of blood draw)

Could cancer be lurking? I'm thinking unlikey but am worried b/c a CT scan of the abdomen was ordered to r/o Lymphoma and see if there are any kidney abnormalities.