免疫标记出来了！

 This is an extremely challenging case.  Gross color, microscopic appearance and immunohistochemical profile are not consistent with renal cell carcinoma, clear cell type.

This tumor is rich in vessels and has focal glomeruloid growth pattern. These are the features of renal cell carcinoma, papillary type. I do not favor urothelial carcinoma.  If this is my case, I would send it to an expert for consultation or call it as renal cell carcinoma, unclassified type.  Renal cell carcinoma, unclassified type is a diagnostic category to which renal carcinoma should be assigned when they do not fit readily into one of the other categories. 

Great discussion! It is an interesting case with focal unique morphologic features. Thanks for the IHC.

• Except peculiar vimentin stain (near the vessels), all other stains are compatible with TCC. CD10 is not a great marker for RCC and has been shown to express in some TCC as well.
• CK stain do highlight papillary core with multiple layers of cells (I interpret them as urothelial cells), multilayering of cells is not a feature with either type 1 or type 2 RCC...I still favor TCC.
• The distinction between different types of RCC may not be terribly important, but distinction between RCC and TCC is important, particularly for younger patient. Before a diagnosis of unclassified RCC (which I do not favor), TCC has to be ruled out. 

透明细胞癌

 I also think that "在肾盂处取材，尤其是正常和肿瘤交界处，看一下是否有癌变的移行处" which is extremely important in this case.  I will be very surprised if urothelial carcinoma involves renal parenchyma, but the renal pelvis does not show any type of urothelial carcinoma.