不同病理亚型肾细胞癌的磁共振成像表现

MR imaging features of different renal cell carcinoma subtypes

目的探讨不同病理亚型肾细胞癌（RCC）的磁共振成像（MRI）表现。方法回顾性分析术前行MRI检查、术后经病理证实的79例患者的81个RCC病灶的影像学表现，比较不同病理亚型RCC在MRI平扫和增强扫描不同时期肿瘤的强化程度与方式、肿瘤侵犯程度以及与手术和病理结果的对照。绘制MRI增强扫描不同时期区分透明细胞癌与非透明细胞癌的操作者特征性曲线，确定用于两者区分的肿瘤实质标准信号噪声比（SNR）值的最佳临界点，进行诊断效价检验。评价不同病理亚型RCC的肾外侵犯程度。结果81个RCC病灶中，透明细胞癌58个，嫌色细胞癌10个，乳头状细胞癌8个，未分类癌5个。T1WI和T2WI序列平扫时，嫌色细胞癌的均质度较高，信号均匀；透明细胞癌的信号不均匀，多为混杂信号。增强扫描时，透明细胞癌主要表现为不均匀强化，嫌色细胞癌主要表现为均匀强化。在增强扫描的皮髓交界期、肾实质期和排泄期，区分透明细胞癌与非透明细胞癌的最佳临界标准SNR值为616、579和278。综合比较，增强扫描肾实质期更利于区分透明细胞癌与非透明细胞癌，其敏感度、特异度、阳性预测值、阴性预测值和准确度分别为62．1％、91．3％、94．7％、48．8％和70．3％。RCC的病理分型与肾外侵犯情况无关。结论不同病理亚型RCC的MRI表现存在差异；MRI检查可以为临床选择个体化的治疗方案及预测疗效提供一定的帮助。

Objective To compare and analyze the MRI features of different renal cell carcinoma （RCC） subtypes. Methods The MR images of 81 surgically and pathologically confirmed renal cell carcinomas from 79 patients were reviewed retrospectively. The MR imaging features of lesions in plain scan, the degree and patterns of lesion enhancement （homogeneous, heterogeneous, peripheral ）, and tumor spreading patterns were analyzed. In order to evaluate the diagnostic validity of differentiating RCC subtypes using signal enhancement, receiver operating characteristic curves （ROC） were generated. The cutoff value of post-contrast signal intensity to noise ratios （SNR） of the tumor parenchyma were also generated in order to differentiate clear cell RCC from other subtypes. Results Of the 81 lesions, 58 were clear cell carcinomas, 10 chromophobe cell carcinomas, 8 papillary cell carcimomas, and 5 unclassified RCC. All the chromophobe cell subtype tumors showed a homogeneous density （ P 〈 0.05 ）. The clear cell subtype tumors were likely heterogenous, and also showed heterogenous enhancement with mixed signal than other subtypes （P 〈 0.05 ）. The cutoff value of SNR, which was used to differentiate clear cell subtype from the other subtypes, were 616 （ corticomedullary phase ）, 579 （ nephrographic phase） and 278 （ excretory phase ）, retrospectively. The nephrographic phase is the most appropriate for differentiation, with a sensitivity of 62.1% , specificity of 91.3% , positive predictive value of 94.7%, negative predictive value of 48.8% and an accuracy value of 70.3%. No significant difference was found in tumor spreading patterns among all subtypes of RCC. Condusion MR imaging features, particularly tumor heterogeneity and degree of enhancement are useful in differentiation of the renal cell carcinoma subtypes, and in choosing an individualized therapy.