Inclusion Criteria:  Renal biopsy diagnosis of MGRS or disease linked to multiple myeloma and B cell lymphoma between 01/01/2010 and 31/12/2020 (for patient group) Renal biopsy diagnosis of nephropathy linked to onco-haematological pathology with full clinical expression (eg Multiple Myeloma, B-cell Lymphoma) between 01/01/2010 and 31/12/2021 (for control group); Age greater than or equal to 18 years; Informed consent freely granted and acquired before the start of the study.  Exclusion Criteria:  Patients who do not meet the relevant inclusion criteria and who do not have an established diagnosis of MGRS or disease related to multiple myeloma and B-cell lymphoma will be excluded from the study.