Association of Radiological Features with Histological Features in Patients with Renal Cell Carcinoma: A Cross-sectional Study

Introduction: Renal Cell Carcinoma (RCC) is a group of neoplastic lesions with unique cytogenetic characteristics and histopathological features. The majority of studies till date on RCC have been focusing on tissue histology to plan neoadjuvant treatment in clinical settings. An accurate forecast of the histopathological subtype has clinical implications in management and response to newer treatment strategies. It is pertinent to preoperatively distinguish a solid renal masses histologically but, there are currently no well-established imaging criteria to classify these tumours on the basis of radiographic evaluation.

Aim: To evaluate the differences in imaging characteristics of different histological subtypes of RCC by Power Doppler Ultrasound and Multi-Detector Computed Tomography (MDCT) scan.

Materials and Methods: This cross-sectional study was conducted in the Department of Urology, Gauhati Medical College and Hospital, Guwahati, Assam, India from March 2016 to December 2017. The study population consisted of 61 patients of RCC who were evaluated with MDCT and Doppler ultrasound prior to surgery and findings were correlated with histopathological forms of tumour. The Pearson Chi-square test and ANOVA test was used to statistically analyse the data.

Results: Histopathology revealed clear cell Renal Cell Carcinoma (ccRCC), chromophobe Renal Cell Carcinoma (chRCC) and papillary Renal Cell Carcinoma (pRCC) in 52, 4 and 5 patients, respectively. Heterogenous enhancement was found in 51 cases and among these 90.4% were ccRCC. Absolute attenuation values in Corticomedullary Phase (CMP) and Nephrographic Phase (NP) for clear cell and chromophobe subtype were higher than papillary subtype, i.e., 88.04±30.40 Hounsfield Unit (HU) and 72.41±20.17 HU for clear cell, 60.75±22.54 HU and 88±16.06 HU for chromophobe; 22.40±12.52 HU and 58.00±4.41 HU for papillary subtype, respectively. Papillary RCC (pRCC) showed a unique enhancement pattern, with a low peak enhancement (average peak of 55.40 HU) and greatest enhancement during the NP. In this study population ccRCC, ChRCC RCC and pRCC had mean Resistive Index (RI) of 0.63±0.06, 0.58±0.0 and 0.67±0.11, respectively.

Conclusion: Power doppler flow imaging is not useful in discriminating subtypes of RCC while multiphasic Computed Tomography (CT) imaging may be useful, particularly the phasic enhancement pattern to distinguish common RCC subtypes which may facilitate treatment planning and choosing appropriate tyrosine kinase inhibitors.