Summary: Observational case report of a 48-year-old woman with primary renal diffuse large B‑cell lymphoma (DLBCL) in Mexico. Interventions: open radical nephrectomy with lymph node dissection (surgical tumor removal). Postoperative therapy: R-CHOP chemoimmunotherapy. Drugs and mechanisms: rituximab (chimeric anti-CD20 monoclonal antibody, B‑cell depletion via CDC/ADCC and apoptosis—immunotherapy), cyclophosphamide (alkylating agent, DNA cross-linking), doxorubicin (anthracycline, topoisomerase II inhibition and DNA intercalation/free radicals), vincristine (vinca alkaloid, microtubule polymerization inhibitor, mitotic arrest), prednisone (glucocorticoid, induces apoptosis of lymphoid cells). Targets: CD20+ malignant B cells, DNA replication/repair, topoisomerase II, microtubules, glucocorticoid receptor–mediated apoptotic pathways.