S100A1 is a
calcium-binding protein, which has been recently found in renal cell
neoplasms. We evaluated the diagnostic utility of immunohistochemical detection of S100A1 in 164 renal cell
neoplasms. Forty-one clear cell, 32 papillary, and 51 chromophobe
renal cell carcinomas, and 40 oncocytomas, 164 samples of normal renal parenchyma adjacent to the
tumors and 13 fetal kidneys were analyzed. The levels of S100A1
mRNA detected by quantitative RT-PCR analysis of frozen tissues from seven clear cell, five papillary, and six chromophobe
renal cell carcinomas, four oncocytomas, and nine samples of normal renal tissues adjacent to
neoplasms were compared with the immunohistochemical detection of
protein expression. Clear cell and papillary
renal cell carcinomas showed positive reactions for S100A1 in 30 out of 41
tumors (73%) and in 30 out of 32 (94%)
tumors, respectively. Thirty-seven renal oncocytomas out of 40 (93%) were positive for S100A1, whereas 48 of 51 (94%) chromophobe
renal cell carcinomas were negative.
S100A1 protein was detected in all samples of unaffected and fetal kidneys. S100A1
mRNA was detected by RT-PCR in all normal kidneys and renal cell
neoplasms, although at very different levels. Statistical analyses comparing the different expression of S100A1 in clear cell and chromophobe
renal cell carcinomas observed by immunohistochemical and RT-PCR methods showed significant values (P<0.001), such as when comparing by both techniques the different levels of S100A1 expression in chromophobe
renal cell carcinomas and oncocytomas (P<0.001). Our study shows that
S100A1 protein is expressed in oncocytomas, clear cell and papillary
renal cell carcinomas but not in chromophobe
renal cell carcinomas. Its immunodetection is potentially useful for the differential diagnosis between
chromophobe renal cell carcinoma and
oncocytoma. Further,
S100A1 protein expression is constantly detected in the normal parenchyma of the adult and fetal kidney.