Primary diffuse large B-cell lymphoma of non-germinal center type with BCL-6 positivity in the kidney: A case report.

Introduction And Importance: Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma, yet primary renal involvement is rare, constituting less than 1 % of renal malignancies. A case of non-germinal center B-cell-like (non-GCB) DLBCL with BCL-6 positivity is particularly unique. Conventionally, BCL-6 is linked to germinal center B-cell-like (GCB) subtypes. This case defies traditional phenotypic classifications, highlighting the diagnostic and therapeutic complexities in treating rare renal lymphomas. Understanding such cases is crucial for improving patient care and advancing lymphoma research.

Case Presentation: A 71-year-old male with left low back pain and hematuria had a 6.4 × 3.2 cm renal mass. Laparoscopic nephrectomy revealed CD20+/PAX-5+/CD38+ DLBCL, classified as non-GCB by the Hans algorithm. Initially stage I, lymphadenopathies and bone lesions post - op led to 5 cycles of R-CHOP, achieving 8-month complete remission.

Clinical Discussion: This first-reported case questions the Hans algorithm's BCL-6-based GCB classification. Pre-op misdiagnosis as renal cell carcinoma stresses pathological confirmation. Lack of PET-CT and molecular profiling limits tumor understanding. R-CHOP's success may relate to BCL-6-mediated chemosensitivity in non-GCB DLBCL.

Conclusion: This rare case emphasizes comprehensive pathological subtyping, PET-CT staging, and molecular profiling. Standardized protocols and long-term follow-up are vital for managing such uncommon lymphoma subtypes.