Characterization and Clinical Impact of the Gut Microbiota in Lymphoma

Inclusion Criteria for the DLBCL cohort: * WHO 2022 classified newly diagnosed and treatment-naïve large B-cell lymphoma (DLBCL) belonging to one of the following entities: * Diffuse large B-cell lymphoma, including transformation from an indolent lymphoma * Follicular lymphoma grade 3B * T-cell/histiocyte-rich LBCL * Primary cutaneous DLBCL, leg type * EBV-positive DLBCL, NOS * Primary mediastinal LBCL * High grade B-cell lymphoma with MYC/BCL2 rearrangement * The patient is a candidate for R-CHOP-like first-line treatment * Staging by PET available before treatment initiation * Age ≥18 years * Written informed consent Exclusion Criteria for the DLBCL cohort: * Pregnancy * Psychiatric illness or condition which could interfere with their ability to understand the requirements of the study * Clinical signs of uncontrolled serious infection * Clinical gastrointestinal lymphoma involvement * Other significant gastrointestinal comorbidities * Any other prior malignancy than non-melanoma skin cancer or stage 0 (in situ), cervical carcinoma, unless treated with curative intent, and without relapse for 2 years, or low-grade prostate cancer, not in need of treatment * Ileostomy * CNS involvement at diagnosis * Severe cardiac disease: NYHA grade 3-4 * Impaired liver (transaminases \> 3 x normal upper limit or bilirubin \> 1.5 x normal upper limit, unless due to Gilbert´s syndrome) or renal (GFR\<30ml/min) function not caused by lymphoma