Benign Renal Epithelial and Mesenchymal Neoplasms and Their Mimics

Abstract

This chronic inflammatory process is an unusual variant of chronic pyelonephritis, associated with renal calculi and commonly found in middle-aged women. The clinical history of recurrent urinary tract infections with flank pain, fever, malaise, anorexia, and weight loss correlates with the discovery of a unilateral renal mass. The “mass” grossly shows marked scarring, pyelocaliceal ectasia, and corticomedullary distortion (Fig. 3.1). These circumstances overlap with true renal malignancy providing a logical clinical basis for FNA and NCB. Morphologically, XPN is an exuberant inflammatory response with an intense mononuclear infiltrate, especially macrophages. The FNA and biopsy will reflect a heterogeneous composition with necrosis, chronic inflammatory cells including numerous macrophages, calcifications, and granulation tissue. Although the foamy, lipid-containing macrophages simulate the clear cells of a renal cell carcinoma, the background of inflammatory cells, necrosis, and calcifications are indicative of a reactive process (Fig. 3.2). The bland, bean-shaped macrophage nuclei are distinguishable from the round nuclei of clear cell renal cell carcinoma. On individual cytologic grounds, this distinction is more difficult for low-grade malignancies. Tumors of higher Fuhrman grade are more easily discerned, since the advancing nuclear pleomorphism also exhibits more vesicular chromatin and nucleolar prominence is more apparent. The acquisition of a core biopsy at the time of FNA will facilitate immunohistochemistry demonstrating the macrophages to be cytokeratin-negative and CD68-positive (Fig. 3.3).