Fine-needle aspiration cytology of bilateral renal malakoplakia.

Isolated bilateral renal malakoplakia in the absence of concomitant involvement of the urinary tract is a rare occurrence. We report imaging, cytologic, and histologic findings of such a case diagnosed initially by fine-needle aspiration (FNA) cytology. A 26-yr-old female presented with pain in the left flank, fever, anorexia, and weight loss for the past 2 mo. A left lumbar lump was palpable on physical examination. Imaging studies showed an enlarged nonfunctioning left kidney and a small lesion in the right kidney with preserved function. FNA from both kidneys yielded purulent material positive for E. coli on culture. The smears were inflammatory, with a predominance of neutrophilic polymorphs and numerous histiocytes along with some intracellular and extracellular Michaelis-Guttman bodies, which were highlighted with the use of a PAS stain. Histology of the nephrectomy specimen showed ill-defined nodules, composed of foamy histiocytes intermingled with neutrophils, plasma cells, and many variably sized concentric laminated bodies. The right-side lesion resolved with the use of broad-spectrum antibiotics in conjunction with ascorbic acid and bethanecol. When imaging studies are suggestive of a chronic inflammatory process, renal malakoplakia must always be considered in the differential diagnosis even if aspirated material shows a predominance of polymorphonuclear leukocytes. The use of special stains like PAS, Von Kossa, and Perl's helps in reaching the correct diagnosis.