The Pathological Features of Leukaemic Cells Infiltrating Renal Interstitium in Chronic Lymphocytic Leukaemia/Small Lymphocytic Lymphoma Within 10 Years in a Large Single Chinese Centre

Background: Chronic lymphocytic leukemia/Small Lymphocytic Lymphoma (CLL/SLL) was rare in Asians and patients with CLL/SLL rarely undergo kidney biopsy. Little information is available on the histopathological features and clinical relevance of CLL/SLL tubulointerstitial injury. Hence, we attempted to describe the clinical characteristics, renal pathology and clinical outcome of a well characterized population of CLL/SLL patients with CLL infiltration in renal interstitium from a large single center in China. Methods: Between January 1st, 2010 to September 31st, 2020, 31946 reanl biopsy pathology were performed at Peking University First Hospital and 10 patients with CLL infiltration in renal interstitium were included. Complete clinical data were collected from these 10 patients and the renal specimens were examined by routine light microscopy, immunonuorescence and electron microscopy examination. Results: The extent of infiltrating CLL cells was diverse between different patients, from 10% to 90%. Five patients presented interstitial infiltration with the percent of infiltrate CLL cells≥50%. Proliferation centers were formed in the renal interstitium of 6 patients (6/10, 60%). Intrestingly, we found three patients (3/10, 30%) expressed monoclonal immunoglobulin in infiltrating CLL cells and special crystal structures were found in these cells in two of the three patients for the first time. Conclusions: The finding confirmed CLL cells infiltrating in renal interstitium can secret monoclonal immunoglobulins directly, indicating that CLL cells in renal interstitium probably directly involved in local lesion injurys by secrecting monoclonal immunoglobulin. This finding will help understanding the mechanism of renal injury with CLL infiltration, thereby improving our current therapeutic efforts.