This renal biopsy is from an adult male patient with history of follicular lymphoma. He notes reduced urine output and fatigue. Laboratory workup reveals an elevated serum creatinine (2.6 mg.dL, baseline SCr normal). A renal biopsy is performed to elucidate the cause of this unexpected change.

The interstitium is expanded by infiltrative sheets of small-to-intermediate lymphoid cells, some with cleaved nuclei. There is no significant large cell population. The residual renal tubules are attenuated with cytoplasmic blebbing and focal loss of brush border, consistent with tubular injury.

Though this lesion is infiltrative and does not display the classic follicular architecture, it was found to be immunophenotypically consistent with the patient's previously diagnosed follicular lymphoma (CD20+, BCL2+, CD10+, CD5-, Ki67 <10%).

Electron microscopy studies, performed on all native kidney biopsies at this instituation, provide a unique view of the cleaved follicular lymphoma cells.