PAX-2 is a helpful marker for diagnosing metastatic renal cell carcinoma: Comparison with the renal cell carcinoma marker antigen and kidney-specific cadherin

Context: The diagnosis of metastatic renal cell carcinoma (RCC) remains problematic. Objective: To evaluate the role of PAX-2, a renal tubular cell transcription factor, in the diagnosis of metastatic RCC. PAX-2 expression in metastatic RCC was compared with that of the renal cell carcinoma marker antigen (RCCM) and kidney-specific cadherin (KSC), which are 2 known markers for RCC. Design: Immunostaining for PAX-2, RCCM, and KSC was performed on consecutive tissue sections of 95 metastatic RCCs (77 clear cell, 8 papillary, 5 sarcomatoid, and 5 collecting duct) and 183 metastatic tumors other than RCC. Results: For PAX-2, positive immunoreactivity was detected in 77% clear cell, 75% papillary, 100% collecting duct, and 0% sarcomatoid metastatic RCCs. For RCCM, positive immunoreactivity was detected in 49% clear cell, 75% papillary, 0% collecting duct, and 0% sarcomatoid metastatic RCCs. For KSC, only 2 metastatic clear cell RCCs (3%) were positive. In combination, all markers were positive in 0% of cases; all markers were negative in 23% of cases (17 clear cell, 1 papillary, and for all 5 sarcomatoid); and at least 1 marker was positive in 76% of cases (PAX-2 only in 28% of cases [21 clear cell, 1 papillary, and 5 collecting duct] and RCCM only in 3% of cases [2 clear, 1 papillary]). Of 183 metastatic tumors other than RCC, 14 were positive for PAX-2 (nodal metastasis of carcinoma of colon [1], breast [1], endometrium [1], and ovary [1]; and omental metastasis of carcinoma of uterus or ovary [10]). Conclusions: PAX-2 is a sensitive and specific marker for metastatic RCC. The diagnostic yield would be marginally increased by adding RCCM, but not KSC, as an immunomarker.