A pure single-disease hem mal position will be hard (not impossible) to come by in a higher paying community/PP position. Even the largest such groups (thinking some of the Texas Onc, Intermountain and PAMF groups) won't have enough pure lymphoma or cellular therapy work to keep you busy all the time, so you'll need to be more broadly focused than that.
If your goal is strictly money, as stated above, a true PP gig where you see everything and maybe work yourself up to be the "lymphoma person" is the best choice. If your goal is a single disease focused practice, academia (with the attendant pay cut) is the surest path.
Another thing to keep in mind is that, at least under current conditions, lymphoma is generally an outpatient practice (with some obvious exceptions) and cellular therapy is generally an inpatient practice (again, with exceptions).