PMC7585650_01
Ultrasound findings: transaxial (a) and long axis (b) views show the right kidney containing a solid, heterogeneous isoechoic mass in the midpole. CT abdomen without IV contrasts coronal (c) and axial (d) views, respectively: a solid isodense mass of the mid to inferior pole of the right kidney protrudes into the renal sinus. There is minimal deformity of the renal contour by the lesion. An incidental cystic lesion of the liver is seen.
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The ultrasound study described it as a "heterogenous isoechoic mass" (Figures 1(a) and 1(b)) after initially being called a "complex renal cyst". A computerized tomography (CT) scan of the abdomen one week prior to surgery concurred and pointed out that despite being protruding into renal sinus, the renal contour was minimally deviated (Figures 1(c) and 1(d)).
P-RCC gross and microscopic findings: (a) grossly, the tumor is less than 7 cm in diameter and confined to Gerota's fascia, making it a stage I tumor. (b) Papillary configuration of the architecture, with (c) necrosis intermittently throughout (100x magnification). (d) Pseudostratification with eosinophilic cytoplasm admixed with foamy histiocytes within a fibrovascular core (400x magnification). These are among the most characteristic features of type 2 papillary renal cell carcinoma.
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The tumor abutted the fatty renal sinus and Gerota's fascia (Figure 2(a)). Histological examination revealed a papillary configuration of pseudostratified cuboidal cells with high nuclear grade and eosinophilic cytoplasm (Figure 2(b)). Tumor necrosis was variably present in different areas (Figure 2(c)). The tumor cell nucleoli were conspicuous and eosinophilic at 400x magnification and visible but not prominent at 100x magnification (Figure 2(d)).
P-RCC immunohistochemistry: (a) CD10, (b) AMACR, and (c) PAX-8 are routinely positive in type II papillary renal cell carcinoma. (d) CK7 displays reactivity in the majority of type 1 papillary renal cell carcinoma, but is found in 20% of type 2 tumors as well (400x magnification).
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By immunohistochemistry, the tumor cells are positive for CD10, alpha-methyacyl-CoA racemase (AMACR), PAX-8, and CK7 (Figure 3).
FSGS: (a) renal cortex with glomerulosclerosis and focal interstitial fibrosis, H&E stain (100x magnification). (b) Global glomerulosclerosis, PAS stain (200x magnification). Normal glomeruli, by definition, must coexist with the pathological process for the diagnosis of FSGS, PAS stain (c) and silver stain (d) (200x magnification). Electron microscopy: (e) foot process effacement, epithelial cell detachment from glomerular basement membrane, and capillary wrinkling (15,000x magnification). (f) Retraction of tufts and wrinkling of capillary walls (12,000x magnification).
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On light microscopy, segmental sclerosis and consolidation of capillary tufts were noted in several viable glomeruli (Figure 4(a)). Rare globally sclerosed glomeruli were also identified (Figure 4(b)). In the viable glomeruli, no crescent, proliferation of capillary cells, or necrosis of capillary tufts was identified (Figure 4(c)). On silver-stained sections, the open capillary loops showed thin and smooth capillary membranes, and no spikes or duplication of capillary membranes was identified (Figure 4(d)). Electron microscopy examination confirmed FSGS with diffuse effacement of podocyte foot processes, epithelial cell detachment from glomerular basement membrane, and capillary wrinkling (Figure 4(e)). Retraction of tufts and wrinkling of capillary walls were noted (Figure 4(f)).