Transitional cell and clear cell renal carcinoma: differentiation of distinct histological types with multiphase CT

Background: Transitional cell carcinoma (TCC) may mimic renal cell carcinoma (RCC) when it develops in a similar location, therefore, differentiation with imaging techniques might be challenging. Preoperative differentiation may have a significant role indicating the type of surgical treatment (nephrectomy vs. ureteronephrectomy). Purpose: To retrospectively analyze the differences in the contrast enhancement of TCC and RCC. Material and Methods: Images of 20 RCC and 12 TCC (mean ages, 62.3 +/- 14.1 and 67.4 +/- 12.0 years, respectively) were analyzed from patients who underwent multiphase computed tomography (CT) examinations following 1.5 mL/kg non-ionic contrast agent administration. Unenhanced corticomedullary (30-45 s), nephrographic (70-90 s), and excretory (300-480 s) phases were imaged. The attenuation characteristics of RCC and TCC were compared to the attenuation of the normal renal cortex. Results: Significant differences were found in the attenuation ratios between RCC or TCC in the corticomedullary (P = 0.040) and nephrographic (P = 0.004) phases using three regions of interest (ROIs) of 10 mm(2) size. If measuring ROIs comprising the complete tumor lesion instead of three small ROIs, no significant difference was observed in the attenuation ratios between RCC in TCC in any phases. Conclusion: Our study reports significant attenuation differences between RCC and TCC in the corticomedullary and nephrographic phases by multiphase CT. The findings underscore the importance of multiphase CT in the differentiation of these two different entities. Using multiple small (three) ROIs is more accurate than measuring the whole tumor attenuation.