MR classification of renal masses with pathologic correlation

Abstract

To perform a feature analysis of malignant renal tumors evaluated with magnetic resonance (MR) imaging and to investigate the correlation between MR imaging features and histopathological findings. MR examinations in 79 malignant renal masses were retrospectively evaluated, and a feature analysis was performed. Each renal mass was assigned to one of eight categories from a proposed MRI classification system. The sensitivity and specificity of the MRI classification system to predict the histologic subtype and nuclear grade was calculated. Subvoxel fat on chemical shift imaging correlated to clear cell type (p < 0.05); sensitivity = 42%, specificity = 100%. Large size, intratumoral necrosis, retroperitoneal vascular collaterals, and renal vein thrombosis predicted high-grade clear cell type (p < 0.05). Small size, peripheral location, low intratumoral SI on T2-weighted images, and low-level enhancement were associated with low-grade papillary carcinomas (p < 0.05). The sensitivity and specificity of the MRI classification system for diagnosing low grade clear cell, high-grade clear cell, all clear cell, all papillary, and transitional carcinomas were 50% and 94%, 93% and 75%, 92% and 83%, 80% and 94%, and 100% and 99%, respectively. The MRI feature analysis and proposed classification system help predict the histological type and nuclear grade of renal masses.

Magnetic resonance imaging as a biomarker in renal cell carcinoma

“…15 In addition to the ability of MRI to accurately characterize renal lesions as neoplasms, [16][17][18][19][20] an ability to noninvasively discriminate the various types of RCC based on their MRI appearances or magnetic resonance phenotypes is achievable. 21,22 The presence of intracytoplasmic vacuoles containing lipids, a histologic characteristic of the clear cell subtype, can be recognized with the use of chemical shift MRI techniques. 23 The presence of intratumoral lipids results in a decrease in signal intensity on T1-weighted, opposed-phase images compared with the in-phase images in the non-necrotic ''viable'' tumor ( Fig.…”

“…Reports on the value of this finding for the correct subtyping of a malignant renal mass as clear cell RCC indicate between 42% and 82% sensitivity and between 94% and 100% specificity. 21,24 The presence of retroperitoneal collaterals, renal vein thrombosis, and intratumoral necrosis on MRI each predict high-grade clear cell subtype, whereas intratumoral necrosis directly relates to tumor size for clear cell carcinomas. 21 A tumor capsule of low signal intensity on T1-and T2-weighted images may be observed, and its interruption is associated with locally advanced disease and higher nuclear grade.…”

“…21,24 The presence of retroperitoneal collaterals, renal vein thrombosis, and intratumoral necrosis on MRI each predict high-grade clear cell subtype, whereas intratumoral necrosis directly relates to tumor size for clear cell carcinomas. 21 A tumor capsule of low signal intensity on T1-and T2-weighted images may be observed, and its interruption is associated with locally advanced disease and higher nuclear grade. 25,26 The majority (85%) of predominantly cystic neoplasms that contain ''simple'' fluid and small solid components and/or thickened or irregular septae represent lowgrade clear cell RCCs.…”

“…25,26 The majority (85%) of predominantly cystic neoplasms that contain ''simple'' fluid and small solid components and/or thickened or irregular septae represent lowgrade clear cell RCCs. 20,21 In contradistinction, cystic neoplasms with hemorrhagic contents and peripheral solid papillary projections are more commonly papillary neoplasms. 21 Papillary carcinomas have other distinct MRI features that correlate with their unique histopathologic characteristics.…”

“…20,21 In contradistinction, cystic neoplasms with hemorrhagic contents and peripheral solid papillary projections are more commonly papillary neoplasms. 21 Papillary carcinomas have other distinct MRI features that correlate with their unique histopathologic characteristics. 27,28 These tend to be located in the surface of the kidney, they are small in size, and they have homogeneous and lower signal intensity compared with the cortex on T2-weighted images.…”