Hello and hope you are doing well.
The other causes for enlarged nodes are tumors or inflammations to name a few. Next you could see if any of the draining areas have any evidence of infection, like tonsils, the skin, tooth abscess or an ear infection. Infections like tuberculosis can cause lymphadenopathy. It would be worthwhile to see if other lymph groups are enlarged namely, axilla and groin, these can be palpated, the others like those in the chest or abdomen may need a CT to detect their enlargement. Also correlate with blood counts, this could lead to further analysis. Sometimes a fine needle may not show much, but a whole node biopsy may pinpoint the cause.
Hope this helped and do keep us posted.