PAX8 (+)/p63 (−) Immunostaining Pattern in Renal Collecting Duct Carcinoma (CDC)

Abstract

We propose the use of the combination of PAX8 and p63 in the diagnosis of poorly differentiated renal sinus epithelial neoplasms where the differential diagnosis includes CDC versus UUC. The immunoprofile of PAX8+/p63- supports the diagnosis of CDC with a sensitivity of 85.7% and a specificity of 100%. In contrast, a (PAX8-/p63+) profile supports the diagnosis of UUC with a sensitivity of 88.2% and a specificity of 100%. The inverse PAX8/p63 expression seen in CDC and UUC supports a renal tubular rather than an urothelial differentiation in CDC given the nephric lineage restriction of PAX8.