- Clear cell renal cell carcinoma
The main characteristic of clear cell RCC is the coexpression of cytokeratins (CK
8/18, 19, 7) and vimentin. Dedifferentiation leads to an increasing expression of
vimentin and finally disappearance of keratins on the immunohistologic level. The
perimembranous positivity changes to a perinuclear (centroplasmic) positivity. The
presence of brush border-associated antigens like villin, CD 10 and CD 13 supports
the proposed histogenetic development from the proximal tubule. A kidney specific
gamma GT antibody, which can be applied on paraffin sections, is helpful in
differential diagnosis of metastatic clear cell, carcinoma of unknown primary as it
proves the renal origin.
- Chromophil renal cell carcinoma
Chromophil RCC have an immunohistologic profile similar to clear cell RCC. The
vimentin expression can be very weak overall but pronounced at the basal cell pole in
the highly differentiated basophilic cell types. Lectins like DBA and SBA are found
in chromophil RCC but not in clear cell RCC. Mab RCC 38 selectively reacts with
chromophil RCC and can serve as a marker for this special kidney tumor type. The
common antigen characteristics are a strong argument for the close relationship
between clear cell and chromophil RCC and their origin from the proximal tubule.
- Renal Oncocytoma
As a rule oncocytomas do not express vimentin, but in central regressive areas they
can show focal vimentin positivity. They also lack antigens of the proximal tubule
and are positive for antigens of the collecting duct, especially those of the
intercalated cells like carbonic anhydrase C and H+ ATPase. The band 3 anion carrier
protein found in type a intercalated cells can be detected only in oncocytomas,
consistent with origin in the collecting duct. While CD 44s can be found on the cell
surface, CD 44v6 is totally absent.
- Chromophobe renal cell carcinoma
Chromophobe RCC are strongly positive for cytokeratin 8/18 and often for CK 7 but
weakly positive for CK 19 and negative for vimentin. They share the positivity for
carbonic anhydrase C and some lectins like DBA, SBA, and WGA with oncocytomas but
lack band 3 anion carrier positivity. Another distinctive feature is the
coexpression of CD 44s and CD44v6 on the cell membrane, which is of differential
diagnostic importance.
- Collecting duct carcinoma
Collecting duct carcinomas may coexpress cytokeratins (CK 8/18) and vimentin. They
show pronounced cytoplasmic positivity for CK 19 and UEA-1 but lack CK 13, antigens
of the proximal tubule and of the intercalated cells. Their columnar epithelial
differentiation is reminiscent of the principal cells of the medullary collecting
duct.
- Urothelial carcinoma
The immunohistological profile of intrarenal urothelial carcinoma differs totally
from those mentioned above. They express cytokeratins typical of both columnar
epithelium(CK 8/18, 19, 7, and 20) and squamous epithelium(CK 5/14/17, and 13) and
lack vimentin. Thus immunohistology favors histogenesis from urothelial cells within
the ducts of Bellini.
- Neuroendocrine tumors of the kidney
The neuroendocrine tumors of the kidney lack vimentin and squamous cell-specific
cytokeratins. They are positive for columnar epithelial cytokeratins (CK 8/18, and
19), and depending on a prevailing endocrine or neurogenic differentiation, may be
positive for chromogranin, synaptophysin, and neurofilaments. These antigens cannot
be detected in any other RCC.
- Metanephic adenoma
In solid tumor areas, the tumor cells express vimentin only whereas in more
differentiated tubular or glomeruloid areas some cytokeratins can be found but not CK
19. Lack of NCAM is of importance for the differential diagnosis of nephroblastoma.
Summing up the data, there is immunohistological diversity among the renal cell
neoplasms. The immunohistological differences reflect the different histogenesis of
the tumors and point to histogenetic relationships in case of common findings (clear
cell RCC and chromophil RCC, oncocytomas and chromophobe RCC).
