It's just a guess, but the person who definitively proves how to prevent lymphoma specifically, to the exclusion of other cancers, that person will be invited to attend a certain prize ceremony in Sweden.
Should they succeed simply in proving how to prevent any cancer (that doesn't involve behavioral modifications), well that too might be enough to earn that invitation.
Unfortunately, as things are, lymphoma might be preventable, but if it is no one knows how and the reason no one knows how is because it is not possible to say how one acquired lymphoma to begin with.
Sure, there are risk factors associated with various subtypes of Hodgkin's lymphoma and non-Hodgkin's lymphoma:
Age: Like many cancers, the older you get the more susceptible you get to developing lymphomas.
Environmental and occupational exposure: The President's Cancer Panel suggests a variety of chemicals that are possible carcinogenic agents associated with lymphoma.
Viral infection: Some subtypes of NHL have been linked to specific viruses. These include HIV and EBV (Epstein-Barr).
Compromised immune system: Auto-immune diseases and other immunocompromises seem to raise the risk of developing some lymphomas.
Gender: Men are slightly more at risk than women.
Genetics: Although there is some evidence that people with siblings who develop Hodgkin's are at greater risk, there is scant evidence that the cancer has a greater genetic link.
However, a person can have none of the risk factors listed above, they can be in good physical shape, and still develop lymphoma. The best that can be said for any cancer is the recommendations from the American Cancer Society, which stresses eating right including lots of fresh fruits and vegetables, exercising regularly and not becoming obese, and not smoking.
photo by John Nyboer