Primary Mediastinal B-Cell Lymphoma and [18F]FDG PET/CT: What We Learned and What Is New.

Primary mediastinal large B-cell lymphoma (PMLBCL) is a rare and aggressive non-Hodgkin lymphoma (NHL), considered a specific entity with proper characteristics, therapies, and prognosis. First-line treatment is not unique, and subsequent strategies in case of disease persistence or relapse are the subject of debate and studies. In this scenario, [18F]FDG PET/CT plays a pivotal role both in characterizing the mediastinal mass, the main feature of PMLBCL, in staging, in restaging during therapy (interim PET), and at the end of treatment (EoT PET), to guide clinical management and give prognostic insights. The main issue with PMLBCL is distinguishing viable disease from residual fibrotic/inflammatory mass after therapy and, consequently, settling the next clinical strategy. Novel therapeutic approaches are ongoing and associated with the deepening of [18F]FDG PET/CT potentials as a principal tool in this context. In this review, we will explore PMLBCL from a Nuclear Medicine point of view to help clinicians in the management of these patients.