ORLANDO, FL USA (UroToday.com) - Commensurate with improved capabilities and understanding of imaging technology and renal tumor histology, some studies have suggested that papillary renal cell carcinoma Type 1 (T1-pRCC) and Type 2 (T2-pRCC) may be distinguished by their behavior and morphology in imaging studies. The authors sought to evaluate the imaging characteristics of T1- and T2-pRCC and their pathological correlates, in order to determine whether multiphase computerized tomography (CT)—and the CT enhancement washout formula—might be utilized in distinguishing between T1 and T2-pRCC subtypes.
The authors retrospectively reviewed 39 patients (T1=18; T2=21) who underwent multiphase CT and surgery at the authors’ institution from 12/2007-7/2012. Pathologic data was analyzed histologically; multiphase CT was analyzed for tumor size, morphology, and attenuation in Hounsfield Units (HU). Change in HU (δHU) was calculated for noncontrast (NC), corticomedullary (CM), nephrographic (N) and delayed (D) phases of the imaging study; from this, the authors calculated the enhancement washout formula (N HU-D HU)/(N HU-NC HU).
No difference was found in median tumor size (T1=2.8 vs. T2=2.0 cm, p=0.520), yet more high-grade tumors (III/IV) were noted in pRCC-T2 (42.9%) than pRCC-T1 (5.6%) (p=0.011). No differences were seen between pRCC subtypes for each of the following variables: frequency of irregular borders, presence of calcifications, presence of necrosis, and heterogeneous enhancement. For δHU, although no difference was observed between CM-NC and D-NC, the δHU measurement at N-NC was distinct (T2=42.7, T1=27.8, p=0.036). The enhancement washout was similar for both (T1=61.1%, T2=52.4%,p=0.584).
Although the T1- and T2-pRCC groups in this study were closely matched by size, key imaging characteristics were very similar, despite the higher proportion of T2-pRCC tumors of high grade. These findings suggest that the utilization of CT to determine between pRCC subtypes should be cautiously exercised, if at all. If pRCC is suspected and providers are considering active surveillance, they should strongly consider percutaneous biopsy in order to confirm the appropriateness of this treatment.
Presented by Michelle McDonald at the American Urological Association (AUA) Annual Meeting - May 16 - 21, 2014 - Orlando, Florida USA
University of California (San Diego) USA
Written by Eric Ballon-Landa, BA, University of California (Irvine), and medical writer for UroToday.com