[Immunohistochemical expression of microvascular density and carbonic anhidrase IX in renal carcinoma. Relation to histological type and tumoral progression]

Purpose: to correlate the immunohistochemical expression of microvascular density (MVD) and the carbonic anhydrase IX (CAIX) with the different histological subtypes of renal carcinoma and its progression.

Material and methods: we studied 93 patients with renal cell carcinoma operated between 1990 and 2008. Antibodies employed for immunohistochemistry (IHC); CD31 (1: 40, Dako) and CD34 (1: 50, Dako) for MVD and CAIX (1: 100, Santa Cruz). CAIX was validated semiquantitatively as: strongly positive (>85%); weakly positive (10% -85%); and negative (< 10%), independently of the intensity of the stain. MVD was validated with both anti-CD31 and anti-CD34 by means of a whole section, to select the microscopic field (x100) with highest density of stained vessels, counting the number of vessels in a photographic field of 0.53 mm(2). Results are expressed as the maximal number of vessels by mm(2) of tumour tissue.

Results: median follow up was 40 months (1-160). We found no differences of expression with any of the 3 IHC markers between tumours that progressed (49) and tumours that did not progress (44). The IHC expression of CAIX was strongly related to MVD, measured for both CD31 and CD34 (p<0.0001). MVD with both antibodies was inversely related to tumour size and Fuhrman grade and was also stronger in clear cell carcinomas compared to the rest of histological subtypes, measured by CD31 (p = 0.001) and CD34 (p = 0.003).

Conclusions: neither MVD nor CAIX expressions were related to tumour progression, but were related to histological subtypes. This fact, added to their co-expression, could prompt the use of the CAIX expression, which is far more reproducible, as a quick and easy approximation to MVD. More research should be done to use it as marker for targeted therapy.