Here's a medical analysis of what he has. Here are some survival statistics. It may not be as much of a non-issue as I first thought. But there are wide variations between individuals and their own forms of cancer, and we should hope, of course, that it doesn't affect Thompson's life and career. A reader with personal experience writes:
At best, the patient lives a normal life of uncertain duration until the disease suddenly becomes aggressive and kills. The usual progress of the disease is as the name implies, slow progression with very few serious symptoms. During this phase, the protocol ten to thirty years ago was Cytoxan (cyclophosphamide) and prednisone, and/or radiation, and "remission" frequently occurred. But the disease invariably returns and recent thinking is to use watchful waiting, rather than aggressive treatment of the slow phase (so as to preserve treatment options until truly needed similar to treatment of HIV). Eventually, the disease progresses to an aggressive stage and paradoxically becomes more responsive to treatments and even cures, but long term survival (cure) of indolent lymphoma is rare.