Sections through the yellow nodules show replacement of renal parenchyma with foamy histiocytes, occasional multinucleated giant cells, and inflammatory cells. The inflammatory cells are composed of lymphocytes, plasma cells, and neutrophils. Lymphoid aggregates are also noted. A few renal tubules are filled with cellular debris and possible bacterial clumps. Features are those of xanthogranulomatous pyelonephritis.
Image courtesy of Jian-Hua Qiao, MD, FCAP, Los Angeles, CA, USA.. Please see case description page for licence and original file information.