The Diagnostic Utility of S100P, PAX8, and P63 in the Differential Diagnosis of Urothelial Carcinoma of the Renal Pelvis and Collecting Duct Carcinoma
Josie Munkberg, Jesse McKenney, Shree Sharma, Neriman Gokden, Roni Cox. University of Arkansas for Medical Sciences, Little Rock, AR; Cleveland Clinic, Cleveland, OH
Background: The distinction between urothelial carcinoma (UCC) and collecting duct carcinoma (CDC) of the kidney is important, as the management and prognosis of patients may differ. Due to overlapping morphologies and location, the differential diagnosis between these two entities can be difficult. Previous studies have reported the use of PAX8 and P63 immunohistochemistry to aid in this differential diagnosis. The goal of the current study is to expand on the usefulness of immunohistochemistry in the diagnosis of CDC vs UCC using the urothelial lineage marker S100P in conjunction with PAX8 and P63.
Design: Departmental archives at two institutions were searched for CDC from 2000-2012. Departmental archives at one of the institutions were searched from 2008-2010 for invasive UCC of the renal pelvis. Cases with available formalin fixed paraffin embedded sections were included, resulting in 5 UCC cases and 4 CDC cases. The slides were subsequently reviewed to confirm the original diagnosis. Immunohistochemistry for S100P, p63, and PAX8 was performed on a representative section of each case using proper positive and negative controls. The percentage of cells with positive staining was scored semiquantitatively as: 0 (no staining), <25% staining (1+), 25-50% staining (2+), >50% staining (3+).
Results: All 4 (100%) of the CDC cases were negative for S100P and p63 and showed 3+ positive nuclear staining for PAX8 (S100P-/p63-/PAX8+). UCC cases showed positive nuclear staining with P63 in all cases (4 with 3+ staining, 1 with 2+). 4 of 5 UCC cases (80%) stained positive with S100P, with 3 cases having 3+ positive nuclear staining and 1 case having 2+ positive nuclear staining. 1 case of UCC was negative for S100P. PAX8 staining was negative in 4 of the 5 (80%) UCC cases, with the remaining case having 1+ positive staining.