[Putative chromophobe cell renal carcinoma: are they or are they not?]

According to the literature, the typical histological findings and simple colloidal iron staining permit the identification of chromophobe cell renal carcinoma, a genetically well-established entity. Our doubts on whether this tumor type can be recognized by conventional methods are presented in this study.

130 cases of renal carcinoma were treated from 1977 to 1997. Of these, 12 showed characteristic general histological features compatible with chromophobe cell renal carcinoma and reticulated and intense, diffuse cytoplasmic positivity on colloidal iron staining. These tumors were reviewed for the following: 1) gross appearance, 2) architecture, 3) cytoplasmic characteristics, 4) nuclear characteristics, 5) colloidal iron histochemical staining which is considered fundamental and exclusive, 6) immunohistochemical phenotype. Ultrastructural study of material fixed in paraffin was also performed.

One case met all 6 criteria, 3 met 5 of them, 6 cases met 4, and 2 cases met 3 of the criteria. The ultrastructural study was not useful in making the diagnosis due to the poor quality of the material.

If all cases were chromophobe cell renal carcinoma, then this tumor type can be recognized and diagnosed by simple techniques in any pathology laboratory, and its incidence, presence of necrosis, hemorrhage and high nuclear grade would be even greater than currently accepted. Furthermore, it would be expected that the prognosis, by each grade and stage, would not be so different from that of the conventional renal carcinoma, as some large series have already indicated. On the other hand, if our cases or some of them were in fact conventional renal cell carcinoma that closely resembled chromophobe cell renal carcinoma, an exact diagnosis cannot be made without a genetic or ultrastructural study (using adequately fixed material), and most of the published studies would therefore have to be questioned.