Discriminating papillary renal cell carcinoma from metanephric adenoma: a quantitative contrast-enhanced CT-based...

Metanephric adenoma (MA) and papillary renal cell carcinoma (pRCC) demonstrate overlapping hypovascular appearances on contrast-enhanced computed tomography (CECT), yet reliable quantitative imaging criteria for their preoperative differentiation are still lacking. This study aimed to evaluate the diagnostic value of quantitative parameters derived from multiphasic CECT for differentiating MA from pRCC.

Ninety-three patients with pathologically confirmed renal tumors (MA, n = 31; pRCC, n = 62) were retrospectively included. CT attenuation values of renal tumors and the ipsilateral renal cortex were measured on unenhanced (UP), corticomedullary (CMP), and nephrographic (NP) phases in all 93 patients, and on the excretory (EP) phase in 84 patients (26 MA, 58 pRCC) as EP images were unavailable in the remaining nine patients. Multiple quantitative parameters were derived. After standardization, univariable and multivariable logistic regression analyses were performed to identify independent predictors, and several multivariable diagnostic models were constructed and compared.

Univariable analysis demonstrated significant differences between pRCC and MA in age, sex, and multiple quantitative parameters derived from the NP and EP. Among these parameters, the absolute tumor enhancement difference between the excretory and unenhanced phases (EP_T-UP_T) showed the highest diagnostic performance [area under the curve (AUC) = 0.885, 95% CI 0.815-0.956]. In multivariable analysis, Model 1 (age, sex, NP_T, EP_T) yielded an AUC of 0.942. Model 2 (age, sex, NP_T-UP_T, EP_T-UP_T) achieved an AUC of 0.944. Model 3 (age, sex, NP_T/C, EP_T/C) demonstrated an AUC of 0.956. Model 4 (age, sex, rNP_T/C, rEP_T/C) achieved the highest diagnostic performance, with an AUC of 0.964. No statistically significant differences in AUC were observed among the four models (all p > 0.05).

Quantitative CECT parameters, particularly those derived from the delayed phases (nephrographic and excretory)-including absolute tumor attenuation values, absolute tumor enhancement differences, absolute tumor-to-cortex ratios, and relative tumor-to-cortex ratios-demonstrate substantial potential for the noninvasive differentiation between MA and pRCC.