[1605] Atypical Lymphocytic Infiltrates of the Kidney: Benign or Malignant?

Christie L Boils, Josephine M Ambruzs, Larry N Cossey, Alexis A Harris, Patrick D Walker, Nidia C Messias. Nephropath, Little Rock, AR

Background: Lymphocytic infiltrates are commonly seen on renal biopsies. They may be diagnostically challenging considering that low grade lymphomas can have similar morphology to reactive infiltrates. Immunohistochemical (IHC) stains for CD3 and CD20 can help sort the diagnostic possibilities of reactive, atypical, and lymphoma. Our aim was to determine if there are histologic features that can distinguish between lymphoma, atypical lymphocytic infiltrates (ALI), and reactive lymphocytic infiltrates (RLI).
Design: Our renal biopsy database was reviewed from 2005 to June 2012. 149 cases with atypical infiltrates were included. Multiple histologic parameters were accessed by reviewing H&E stained sections and IHC stains for CD3 (T-cells) and CD20 (B-cells). Percentages of T-cells and B-cells were estimated within lymphocytic infiltrates of concern. Histologic features were compared among those cases classified as lymphoma, ALI, and RLI.
Results: Of these 149 cases, 34 were diagnosed as lymphoma, 20 ALI, and 95 RLI. Similar among these groups was the distribution of the infiltrate as diffuse vs. patchy, cortical and medullary involvement, and tubulitis. Lymphoma cases were more likely to be monotonous (53%) compared to ALI (24%) and RLI (25%), present away from areas of interstitial fibrosis/tubular atrophy (40% vs. 21% and 26%, respectively), involve perirenal soft tissue (77% vs. 28% and 43%), and have a destructive quality (40% vs. 3% and 15%). Of the RLI, the lymphoid infiltrate showed either a mixture of T- and B-cells or a predominance of T-cells in 96% of cases, with mean percentage of 68% T-cells and 32% B-cells. The atypical cases had mixed or T-cell predominate infiltrates in 70% of cases with mean percentage of 46% T-cells and 54% B-cells. Excluding 3 cases of T-cell lymphomas, the remaining 33 lymphoma cases all showed B-cell predominance, with mean percentage of 13% T-cells and 87% B-cells.
Conclusions: In our series, monotonous cytology, extension into perirenal soft tissue, destruction of renal architecture, and greater discrepancy between CD3 and CD20 populations were more common in lymphoma. However, the morphologic overlap observed between reactive and neoplastic infiltrates is noteworthy. Reactive infiltrates can still show marked destruction of renal architecture. Monotonous infiltrates can show a mixed population of T-cells and B-cells, suggesting a reactive nature. These findings emphasize the importance of having a high index of suspicion based on biopsy findings and using CD3 and CD20 IHC stains for triage in order to determine which atypical lymphocytic infiltrates warrant further hematopathologic evaluation for lymphoma.
Category: Kidney (does not include tumors)

Monday, March 4, 2013 1:00 PM

Poster Session II # 231, Monday Afternoon

 

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