Renal Pathology Society/International Kidney and Monoclonal Gammopathy Research Group consensus on pathologic definitions and terminology of monoclonal gammopathy-associated kidney lesions.

The spectrum of kidney lesions associated with monoclonal gammopathy has significantly expanded over the past 2 decades, with description of new entities and variants of old entities. Pathologic diagnosis is challenging because of lesional complexity, heterogeneity, and reliance on electron microscopy and ancillary techniques. A lack of precise pathologic definitions and uniform terminology has hampered diagnostic accuracy. To address these challenges, the Renal Pathology Society and International Kidney and Monoclonal Gammopathy Research Group jointly tasked a working group of nephropathologists and nephrologists to establish consensus-based terminology and definitions for monoclonal gammopathy-associated kidney lesions. Participants included experts in the field with international representation. This report presents their recommendations. For each lesion, prerequisite (mandatory) diagnostic criteria and supportive (nonmandatory) features are proposed. New terminology is provided for some lesions. Application of standardized terminology and definitions should help harmonize kidney biopsy diagnosis with precision therapy in the monoclonal gammopathy-associated kidney disorders.