Can agent orange cause diffuse large b cell lymphoma?

No one knows. Certainly some other cancers have been linked but as far as i know there is no direct linkage. On the other hand, herbicides have had an association with lymphoma and myeloma and agent orange is a "super herbicide". It is always hard to show a direct linkage.
It is associated. Lymphomas are on the list of cancers associated with agent orange. Veterans exposed to agent orange who develop lymphomas are eligible for benefits from the va.