Clinico-radio-pathologic features of a solitary solid renal mass at MDCT examination

Background: Incidental detection of solid renal masses has been increasing since the multidetector computed tomography (MDCT) scanner was introduced. Purpose: To evaluate the clinico-radio-pathologic features of a solitary solid renal mass at MDCT examination. Material and Methods: A total of 466 non-fatty solid renal masses in 466 patients undergoing nephrectomy were evaluated by MDCT examination. MDCT was performed before and after intravenous injection of contrast material. We obtained the incidences of benign tumors versus malignant tumors, renal cell carcinoma (RCC) versus non-RCC, and asymptomatic RCCs versus symptomatic RCCs. MDCT accuracy for detection of RCC was obtained with a threshold of more than 20 HU tumor attenuation difference between unenhanced and contrast-enhanced CT images. Nuclear grade was also compared between small RCCs (=4 cm) and large RCCs (>4 cm). Results: Of 466 tumors, 443 (95%) were malignant and 23 (5%) were benign. Of 443 malignant tumors, 437 (99%) were RCC and 6 (1%) were non-RCC. Of 437 RCCs, 324 (74%) were asymptomatic and 113 (26%) were symptomatic. Asymptomatic RCCs (n=183, 56%) were more frequently pT1a than symptomatic RCCs (n=28, 25%) (P<0.05). MDCT accuracy for detection of RCC was 94% (437/466). Of 220 RCCs =4 cm, low grade RCC (53%) was more common than high grade RCC (47%). Conclusion: Most solitary solid renal masses are early stage RCCs and can be diagnosed preoperatively at MDCT examination.