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case_images: Contrast-enhanced CT of the dilated renal pelvis and mural nodular lesions. The dilated renal pelvis is the main part of the lesion and renal parenchyma thinning (A). Irregular soft tissue parts with gradual enhancement at the wall of the dilated pelvis are shown arrows, (B) arterial phase; (C) delayed phase.
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case_images: The plain and contrast-enhanced CT demonstrated a mass measuring 120 mm in diameter in the left kidney (Figure 1A). There was also a gradual enhancement of the irregular soft tissue parts of the mass on dynamic contrast-enhanced CT (Figure 1B,C).
case_images: Contrast-enhanced MRI on the arterial phase showing an irregular soft tissue part (arrows) with contrast enhancement (A) and restricted diffusion (B), diffusion-weighted image (b = 800); (C) apparent diffusion coefficient (ADC) map, (ADC = 0.9-1.1 x 10-3 mm2/s).
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case_images: A low signal intensity on T2-weighted images located at the solid portion of the mass showed gradual enhancement on dynamic contrast-enhanced MRI and diffusion restriction (apparent diffusion coefficient = 0.9-1.1 x 10-3 mm2/s) (Figure 2A-C).
case_images: Retrograde pyelography showing the continuity between the ureter and the dilated pelvis forming the main part of the tumor.
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case_images: Retrograde pyelography was performed, which revealed continuity between one of the ureters and the dilated pelvis forming the main part of the mass (Figure 3).
case_images: Exophytic papillary lesions along the wall of the dilated pelvis (arrows) compared between a CT image (A) and a macroscopic specimen (B); mucus has already been drained.
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case_images: Gross pathological specimens demonstrated a mass measuring approximately 14 cm in diameter (Figures 4 and 5). An irregular solid nodule was identified alongside the wall of the dilated pelvis (Figure 4B) and extended to the pyeloureteral junction (Figure 5B).
case_images: Correlation between CT and a gross pathological finding of stenosis of the pyeloureteral junction due to the presence of the tumor (arrows), (A) contrast-enhanced CT image; (B) macroscopic image and the dilated renal pelvis (asterisks).
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case_images: Gross pathological specimens demonstrated a mass measuring approximately 14 cm in diameter (Figures 4 and 5). An irregular solid nodule was identified alongside the wall of the dilated pelvis (Figure 4B) and extended to the pyeloureteral junction (Figure 5B).
case_images: Histopathology of villous adenoma of the renal pelvis and pyeloureteral junction revealing typical villous structures. The villi replace the urothelium of the ureter without stromal invasion (A; hematoxylin and eosin [H&E], x20). An adenomatous polyp composed of closely packed slender villi lined by columnar epithelium with intracellular mucin (B; H&E, x100). Mucinous adenocarcinoma with abundant mucin (C; H&E, x40). Mucinous adenocarcinoma with enlarged, hyperchromatic nuclei (D; H&E, x200).
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case_images: The microscopic examination revealed that the surface of the mass was composed of villous components with irregular folding and exophytic growth (Figure 6A). Within the dilated renal pelvis and contiguous ureter, the tumor had villous structures lined by atypical columnar epithelium and many of the cells had intracellular mucin (Figure 6B). Mixed in with this, the invasive component was observed focally in the form of mucinous adenocarcinoma with abundant extracellular mucin, dissecting the stroma of the renal pelvis wall (Figure 6C,D).
case_images: Sequence analyses of genetic mutations (A; GNAS [R201H] mutation [wild type; CGT], B; KRAS [G13D] mutation [wild type; GGC]) by the reverse-transcription polymerase chain reaction method.
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case_images: In addition, genetic analyses revealed GNAS and KRAS mutations of the tumor in the pelvis and urethra (Figure 7).