Fig. 4

Histological findings in the surgical specimen. The tumor shows an invasive growth pattern (a; scale bar = 200 μm, hematoxylin and eosin [H&E] staining; × 10) and solid/diffuse proliferation of highly atypical urothelial-like cells with large, irregular, and pleomorphic nuclei (b; scale bar = 50 μm, H&E staining, × 40). Apparent keratinization was only partly observed. c; scale bar = 200 μm, H&E staining, × 10). Non-neoplastic uroepithelium (left) and adjacent focus of urothelial carcinoma in situ (right) are present in the renal pelvis. d; scale bar = 500 μm, H&E staining, × 4)