Molar Ratio of Free Light Chain to Monoclonal Protein as a Potential Prognostic Marker in Intact Immunoglobulin Multiple Myeloma

This brief report addresses intraclonal heterogeneity in multiple myeloma (MM) through a laboratory-based exploratory approach. We conducted a retrospective study of 49 patients with intact immunoglobulin MM and abnormal serum free light chain (sFLC) ratio at diagnosis, evaluating the molar relationship between sFLC and monoclonal protein (MP). The relative excess of sFLC showed wide variability, and higher values were associated with a trend toward less favorable outcomes, although not statistically significant. These findings suggest that the sFLC-to-MP relationship may reflect underlying biological features related to intraclonal heterogeneity and provide additional insight beyond conventional assessment.