Pax-2 expression in adult renal tumors

To assess the expression of the homeogene Pax-2 in adult renal cell carcino mas, we did a retrospective immunohistochemical analysis of 56 frozen tunor samples representing all major histologic subtypes of renal tumors. There were 33 conventional renal cell carcinomas (58.9%), 12 papillary renal cell carcinomas (21.4%), 4 chromophobe cell renal carcinomas, 4 urothelial cell renal carcinomas, and 3 oncocytomas. Forty-five tumors (62.5%) were locali zed, and 21 tumors had extrarenal involvement. Eight patients (14%) had met astatic disease at the end of the follow-up. We searched for relationships between Pax-P expression and nuclear grading, TNM staging, Ki-67 proliferat ion index, expression of transforming growth factor-beta1 (TGF-beta1), an i n vitro down-regulator of Pax-2 expression, and finally cytogenetic abnorma lities. All histologic subtypes expressed Pax-2 protein, except urothelial renal carcinomas. The highest expression was in papillary renal cell carcin omas. In this subtype, all tumors and 83.3% +/- 12.3% of tumor cells were i mmunoreactive for Pax-2. All but 2 conventional renal fell carcinomas expre ssed Pax-P, but with 26.3% +/- 29.6% of immunoreactive cells (P < .001). Pa x-2 expression was not correlated with nuclear grading (P = .6), tumor size (P = .3), and TGF-<beta>1 expression (P = .1). Nevertheless, Pax-P express ion correlated with the Ki-67 proliferation index only for the conventional histologic subtype (P = .03). In this histologic subtype, Pax-2 expression was higher in patients with metastatic disease than in those without (P = .02). Pax-2 expression was not associated with specific cytogenetic abnorma lities like trisomy 7 (P = .1), 3p deletion (P = .5), and hyperdiploidy (P = .2). TGF-beta1 expression, positive in 33 tumors (59%), was not correlate d with either Pax-P expression (P = .1) or current prognostic factors such as nuclear grading (P = .2). Interestingly, we also observed an expression of TGF-beta RI and TGF-beta RII in the tumors with high nuclear grading (P = .005). We conclude that Pax-P protein is expressed in all major histologi c subtypes of renal cell carcinomas. The pattern of expression differs betw een these subtypes, Pax-P expression in conventional renal cell. carcinomas is correlated with the proliferation index and is significantly higher in patients with metastatic disease. HUM PATHOL 32: 282-287. Copyright (C) 200 1 by W.B. Saunders Company.