LAUSR

A 66-year-old woman with a past medical history of stroke, hypertension and right carotid stenosis presented with renal insufficiency. A CT scan demonstrated left renal atrophy and a 15-cm heterogeneous, solid and cystic enhancing mass occupying most of the right kidney. She underwent CT guided fine needle aspiration of the right renal mass with rapid on-site evaluation (ROSE). Six passes were performed, but only cyst fluid and rare macrophages were seen on ROSE. Since these findings were felt not to be representative of the mass, a core biopsy was obtained and showed nucleolar (ISUP) grade II clear cell renal cell carcinoma (CCRCC). Papanicolaou and Diff-Quik stained aspirate smears and hematoxylin and eosin (H&E) stained cell block sections confirmed the lack of epithelial cells on the cytology specimen and showed, in addition to debris and rare macrophages, spherical structures measuring 60-100 μm in diameter. In Papanicolaou stained smears, these structures had a central “starburst” refractile orange core and peripheral glassy and homogenously cyanophilic staining (Figure 1). In Diff-Quik stained smears, these structures showed a yellow staining core that was separated by a thin blue ring from the lavender-colored, homogenous periphery (Figure 2). While only a few of these spherical structures were present in the smears, the cell block sections showed numerous spherical structures measuring 50-130 μm in diameter (Figure 3). The spherical structures stained pink to purple with H&E, showed a darker core, separated by one or two distinct rings from their paler zone periphery. They had a fuzzy border and fibrillary appearance with thin fibrils radiating from the central core. The spherical structures did not stain with Masson's trichrome, periodic acid-Schiff (PAS), Congo red or Gömöri methenamine silver (GMS) and were interpreted as Liesegang rings. In addition to Liesegang rings, the smears and cell block sections also showed bundles and aggregates of apparently branching, disorganized ribbon-like structures measuring about 2 μm in width and 20-40 μm in length. These structures stained with PAS, but not with GMS, and were interpreted as pseudofungi (Figure 4). “Liesegang rings” are named in honor of Raphael Eduard Julius Liesegang (1869-1947), a German chemist, poet and pioneer of color photography and television. Liesegang first noticed the phenomenon in 1896, while working in his father's photography factory. He observed the formation of concentric rings of silver dichromate after placing a drop of silver nitrate at the center of gelatin impregnated with ammonium dichromate. The phenomenon immediately attracted the attention of the scientific community from different fields and soon Wilhelm Ostwald (1853-1932), one of the founders of physical chemistry and a 1909 Nobel-prize winner referred to it as “Liesegang rings.” The phenomenon occurs widely in nature and is frequently