PMC5820550_01
Computed tomogram of the abdomen-pelvis with contrast shows a 4.5 x 3.3 cm heterogeneous, enhancing soft-tissue density mass within the right kidney with a patent right renal vein (white arrow).
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A CT with contrast confirmed the 4.5 x 3.3 cm heterogeneous, enhancing soft tissue right renal mass with patent renal vein and no retroperitoneal lymphadenopathy (Figure 1).
Positron emission tomography shows an intensely fluorodeoxyglucose-avid right renal mass with imaging characteristics highly suspicious for renal cell carcinoma (white arrow).
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T1/T2 hypointense, diffusion-restricting, right mid-renal mass very suspicious for RCC. The patient subsequently underwent a staging positron emission tomography-CT that showed an intensely fluorodeoxyglucose-avid right renal mass (standard uptake value = 14.3) (Figure 2).
Renal mass pathology shows multiple renal abscesses with filamentous structures (red arrow) on hematoxylin and eosin stain under (a) low power (40x) and (b) high power (100x). Gomori's methenamine silver stain shows no fungal hyphae but highlights the filamentous bacterial forms (black arrow) under (c) low power (40x) and (d) high power (100x). These filamentous bacteria stain weakly positive with Fite's stain supporting the diagnosis of Nocardia species (yellow arrow) under low power (40x) (e) and high power (100x) (f).
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Methenamine silver stain showed filamentous bacteria-like structures staining positive on gram stain which were weakly positive on the Fite staining method, supporting a diagnosis of Nocardia renal abscess (Figure 3).