Renal interstitial infiltration by non-Hodgkin lymphoma: clinicopathological features, outcomes, and prognostic markers from a Chinese biopsy cohort.

Renal involvement by non-Hodgkin lymphoma (NHL) is under-recognized and often misdiagnosed as interstitial nephritis. Kidney biopsy remains the gold standard for confirming lymphoma interstitial infiltration. Currently, the histopathological characteristics of lymphoma-related renal interstitial infiltration and their relationship with clinical prognosis remain unclear. We retrospectively analyzed 36 biopsy-proven cases to characterize clinicopathological features, prognostic markers such as tubular basement membrane (TBM) deposits and patient outcomes. Clinicopathological data were collected at the time of kidney biopsy. The cohort included 21 males and 15 females, with a median age of 65 years (range: 19-84). Among them, 26 had indolent B-cell NHL, seven had aggressive B-cell NHL, and three had T-cell NHL. In indolent B-cell NHL, lymphoma infiltration ranged from 10 to 90%. Glomerular lesions were observed in 23 patients (23/26, 88.5%). TBM deposits were found by electron microscopy in four patients. Notably, TBM immune deposits were associated with worse kidney outcomes (p = 0.03). In aggressive B-cell and T-cell NHL, diffuse interstitial infiltration was prominent, resulting in acute kidney injury (AKI) and kidney enlargement. T-cell NHL was linked to poorer kidney outcomes and overall survival (p < 0.001). In conclusion, different lymphoma types exhibited different kidney lesions, with T-cell NHL was associated with worse outcomes. TBM deposits were associated with poor kidney prognosis in indolent B-cell NHL. Our findings highlight that the presence of a diffuse, monomorphic interstitial infiltrate-particularly when accompanied by invasion of sclerotic glomeruli or the renal capsule-should raise strong suspicion for lymphomatous infiltration over interstitial nephritis.