The Role of Dynamic CT in The Differential Diagnosis of Renal Mass and Determination of the Renal Cell Carcinoma Subtype

Abstract

Objective: We aimed to differentiate oncocytoma from renal cell carcinoma (RCC) and to define subtypes of RCC by using density level of tumors from pre-operative contrast-enhanced dynamic CT. Method: The records of patients who underwent total or partial nephrectomy because of a renal mass in our hospital between 2014-2018 were examined retrospectively. CT scans were performed in non-contrast, arterial, venous and late venous phases with the 4-phase Dynamic Abdominal CT protocol. One general radiologist evaluated the images blinded to pathology. Tumor size (cm), heterogeneous-homogenous characteristic features of tumor composition, and tumor margins, involvement of collecting system, calcification, necrosis, accompanying LAP or thrombosis and mass attenuation values were noted. Results: In the study population of 38 patients, 22 clear cell carcinoma (n=22), papillary cell carcinoma (n=6), chromophobe cell carcinoma (n=5), and oncocytoma (n=5) were detected. The mean tumor diameters were 6 cm in clear cell RCC, 10.9 cm in chromophobe cell RCC, 3.7 cm in papillary cell RCC and 4.4 cm in oncocytoma. Bleeding in a clear cell RCC, septation in 2 clear cell RCC, local invasion in one clear cell RCC, and calcification in one clear cell RCC were noted. No metastasis, LAP and venous thrombosis were found. HU values of papillary cell carcinoma in arterial and venous phases were lower than clear cell RCC (p=0.001, p=0.016). Also HU values of oncocytoma in late phase were higher than clear cell carcinoma (p=0.019). Conclusion:The spectrum of differential diagnoses can be narrowed by the attenuation values obtained by using Dynamic CT in kidney masses. Oncocytoma with high HU levels and papillary cell carcinoma with low HU levels should be considered in the priority order.