Renal tumors with low signal intensities on T2-weighted MR image: radiologic-pathologic correlation

Radiologic and pathologic correlation of a renal venous hemangioma

Renal hemangiomas, including the rare subtype of venous hemangioma, are typically non-cancerous, often asymptomatic, and usually discovered incidentally during imaging studies. Here, we report a unique case of a 59-year-old African-American female with a renal venous hemangioma that initially mimicked papillary-type renal cell carcinoma (RCC-pt) on imaging studies. The patient's presentation included a long history of rectal bleeding and an incidental discovery of a hypoattenuating mass in the left kidney during a contrast-enhanced CT scan. Renal MRI revealed a 3.5 cm left renal lower pole mass, presenting as heterogeneously hyperintense on T1-weighted images and hypointense on T2-weighted images, with gradual mild enhancement post-contrast. Subsequent total nephrectomy confirmed the histopathological diagnosis of a venous hemangioma. This case underlines the need for recognizing unique imaging features of renal venous hemangiomas, contributing to the differential diagnosis of T2 dark hypoenhancing renal masses. Correct interpretation may prevent unnecessary invasive procedures and operations, thereby improving patient management and outcomes.

MRI Characteristics of Pediatric and Young-Adult Renal Cell Carcinoma: A Single-Center Retrospective Study and Literature Review

Pediatric renal cell carcinoma (RCC) is a rare malignancy. Magnetic resonance imaging (MRI) is the preferred imaging modality for assessment of these tumors. The previous literature has suggested that cross-sectional-imaging findings differ between RCC and other pediatric renal tumors and between RCC subtypes. However, studies focusing on MRI characteristics are limited. Therefore, this study aims to identify MRI characteristics of pediatric and young-adult RCC, through a single-center case series and literature review. Six identified diagnostic MRI scans were retrospectively assessed, and an extensive literature review was conducted. The included patients had a median age of 12 years (63-193 months). Among other subtypes, 2/6 (33%) were translocation-type RCC (MiT-RCC) and 2/6 (33%) were clear-cell RCC. Median tumor volume was 393 cm³ (29-2191 cm³). Five tumors had a hypo-intense appearance on T2-weighted imaging, whereas 4/6 were iso-intense on T1-weighted imaging. Four/six tumors showed well-defined margins. The median apparent diffusion coefficient (ADC) values ranged from 0.70 to 1.20 × 10^-3 mm²/s. In thirteen identified articles focusing on MRI characteristics of MiT-RCC, the majority of the patients also showed T2-weighted hypo-intensity. T1-weighted hyper-intensity, irregular growth pattern and limited diffusion-restriction were also often described. Discrimination of RCC subtypes and differentiation from other pediatric renal tumors based on MRI remains difficult. Nevertheless, T2-weighted hypo-intensity of the tumor seems a potential distinctive characteristic.

Free-breathing BLADE fat-suppressed T2 weighted turbo spin echo sequence for distinguishing lung cancer from benign pulmonary nodules or masses: A pilot study

OBJECTIVE

Diffusion Weighted Imaging (DWI) can be used to differentiate benign and malignant pulmonary nodules or masses, while T2WI is also of great value in the differential diagnosis of them. For example, T2WI can be used to differentiate abscess from lung cancer. The study aims to quantitatively evaluate the efficacy of free-breathing BLADE fat-suppressed T2 weighted turbo spin echo sequence (BLADE T2WI) for differentiating lung cancer (LC) and benign pulmonary nodule or mass (BPNM).

METHODS

A total of 291 patients with LC (197 males, 94 females; mean age 63.2 years) and 74 BPNM patients (53 males, 21 females; mean age 62.8 years) who underwent BLADE T2WI at 3-T MRI between November 2016 and May 2022were included in this retrospective study. Two radiologists independently blinded observed the MR images and measured the T2 contrast ratio (T2CR). Mann-Whitney U test was used to compare T2CR values between the two groups, ROC curves were used to evaluate the diagnostic efficacy of BLADE T2WI.

RESULTS

The two radiologists had good inter-observer consistency for T2CR (ICC = 0.958). The T2CR of BPNM was significantly higher than LC (all p < 0.001); the cut-off value of T2CR was 2.135, and the sensitivity, specificity, and accuracy of diagnosis were 75.6%, 63.5%, and 73.2%, respectively. Moreover, T2CR correctly diagnosed 220 LC cases (220/291 = 75.6%) and 47 BPNM cases (47/74 = 63.5%).

CONCLUSION

The T2CR value of MR non-enhanced BLADE T2WI can be easily obtained and can quantitatively distinguish BPNM from LC, thus avoiding misdiagnosis caused by lack of work experience.

Renal Parenchymal Leiomyoma Mimicking Renal Cell Carcinoma: A Case Report

BACKGROUND

Renal leiomyoma is a challenging diagnostic and therapeutic condition. Given that 90% of leiomyomas originate from the renal capsule, leiomyoma presenting as a renal parenchymal mass is extraordinarily rare.

CASE PRESENTATION

Herein, we report the clinical and imaging features of a patient with renal leiomyoma occurring in the renal parenchyma and mimicking renal cell carcinoma. We also review the clinical, imaging, and histological features of renal leiomyoma.

CONCLUSION

An initial partial, simple or radical nephrectomy according to tumor size and patient's underlying condition is suitable for larger, heterogeneous, and non-peripherally located tumors, even if they demonstrate hypointensity on T1- and T2-weighted images, considering the possibility of other diagnoses.

Deep learning with a convolutional neural network model to differentiate renal parenchymal tumors: a preliminary study

PURPOSE

With advancements in medical imaging, more renal tumors are detected early, but it remains a challenge for radiologists to accurately distinguish subtypes of renal parenchymal tumors. We aimed to establish a novel deep convolutional neural network (CNN) model and investigate its effect on identifying subtypes of renal parenchymal tumors in T2-weighted fat saturation sequence magnetic resonance (MR) images.

METHODS

This retrospective study included 199 patients with pathologically confirmed renal parenchymal tumors, including 77, 46, 34, and 42 patients with clear cell renal cell carcinoma (ccRCC), chromophobe renal cell carcinoma (chRCC), angiomyolipoma (AML), and papillary renal cell carcinoma (pRCC), respectively. All enrolled patients underwent kidney MR scans with the field strength of 1.5 Tesla (T) or 3.0 T before surgery. We selected T2-weighted fat saturation sequence images of all patients and built a deep learning model to determine the type of renal tumors. Receiver operating characteristic (ROC) curve was depicted to estimate the performance of the CNN model; the accuracy, precision, sensitivity, specificity, F₁-score, and area under the curve (AUC) were calculated. One-way analysis of variance and χ² tests of independent samples were used to analyze the variables.

RESULTS

The experimental results demonstrated that the model had a 60.4% overall accuracy, a 61.7% average accuracy, and a macro-average AUC of 0.82. The AUCs for ccRCC, chRCC, AML, and pRCC were 0.94, 0.78, 0.80, and 0.76, respectively.

CONCLUSION

Deep CNN model based on T2-weighted fat saturation sequence MR images was useful to classify the subtypes of renal parenchymal tumors with a relatively high diagnostic accuracy.

Renal Angiomyolipoma Based on New Classification: How to Differentiate It From Renal Cell Carcinoma

OBJECTIVE

The purpose of this article is to describe useful imaging features for differentiating angiomyolipoma (AML) subtypes from renal cell carcinoma subtypes.

CONCLUSION

A newer radiologic classification of renal AML consists of fat-rich AML (≤ -10 HU), fat-poor AML (> -10 HU; tumor-to-spleen ratio < 0.71; signal intensity index, > 16.5%), and fat-invisible AML (> -10 HU; tumor-to-spleen ratio, > 0.71; signal intensity index, < 16.5%). Each subtype must be differentiated from the renal cell carcinoma subtype because of overlapping imaging features.

Magnetic resonance imaging findings of renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion in adults: a pilot study

PURPOSE

The purpose of the study was to retrospectively analyze MRI findings of renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2/TFE RCC) in adults.

METHODS

Sixteen patients with Xp11.2/TFE RCC were reviewed retrospectively. The clinical characteristics and imaging features were assessed and then compared between metastatic and non-metastatic subgroups.

RESULTS

The mean age at diagnosis was 47.4 (20-76) years. Seven (44 %) patients were men, and nine (56 %) patients were women. The lesions predominantly exhibited an endophytic distribution (n = 14, 88 %) with a capsule (n = 16, 100 %), accompanied by solid and cystic patterns (n = 12, 75%) and hemorrhage (n = 11, 69 %). The tumors prevalently appeared hyper- to isointense on T1WI (n = 14, 88 %), hypointense on T2WI (n = 13, 81 %), and hyperintense on DWI (n = 16, 100 %) with a lower ADC (P < 0.001) than that of the surrounding tissue. The tumors were less enhanced than the normal renal cortex in all phases with a prolonged enhancement pattern (P ≤ 0.001). In addition, six patients (38 %) developed recurrence or metastases. The RCCs with metastases showed an irregular shape (P = 0.013), an incomplete capsule (P = 0.018), heterogeneous solid-cystic patterns (P = 0.034), and hemorrhage (P = 0.037) than non-metastatic subgroups.

CONCLUSIONS

MRI provides valuable information for the diagnosis of adult Xp11.2/TFE RCCs. Features including irregular shape, incomplete capsule, mixed solid-cystic pattern, and hemorrhage may indicate the occurrence of recurrence or metastases.

Quantitative multiparametric MR analysis of small renal lesions: correlation with surgical pathology

PURPOSE

The purpose of the study is to evaluate the utility of apparent diffusion coefficient (ADC), chemical shift signal intensity index (SII), and contrast enhancement in distinguishing between benign lesions and renal cell carcinoma (RCC) and between subtypes of renal lesions.

METHODS

This retrospective study included 98 renal lesions (≤ 3 cm) on MRI with correlative surgical pathology. Scanner field strength, lesion location, and size were recorded. Two readers blinded to surgical pathology independently measured ADC ratio (ADC lesion/ADC non-lesion kidney), SII, and absolute/relative enhancement in the corticomedullary and nephrographic phases of contrast.

RESULTS

There were 76 malignant and 22 benign lesions. 42 RCC were clear cell (ccRCC), 19 papillary (pRCC), 5 chromophobe (cbRCC). Benign lesions included both solid and cystic lesions. Interreader agreement for all variables was good-excellent (ICC 0.70-0.91). There was no difference in ADC or SII between benign and malignant lesions. There was greater absolute corticomedullary enhancement of benign versus malignant lesions (150.0 ± 111.5 vs. 81.1 ± 74.8, p = 0.0115), which did not persist when excluding pRCC. For lesion subtype differentiation, ADC_ratio for pRCC was lower than benign lesions (0.74 ± 0.35 vs. 1.03 ± 0.46, p = 0.0246). ccRCC demonstrated greater SII than other RCC (0.09 ± 0.22 vs. 0.001 ± 0.26, p = 0.0412). Oncocytomas and angiomyolipoma (AML) showed greater absolute corticomedullary enhancement than ccRCC and pRCC (145.6 ± 65.2 vs. 107.2 ± 85.3, p = 0.043 and 186.2 ± 93.9 vs. 37.6 ± 35.3, p = 0.0108), respectively.

CONCLUSIONS

While corticomedullary-phase enhancement was a differentiating feature, quantitative metrics from diffusion and chemical shift imaging cannot reliably differentiate benign from malignant lesions. Quantitative assessment may be useful in differentiating some benign and malignant lesion subtypes.

Renal epithelioid angiomyolipoma: magnetic resonance imaging characteristics

OBJECTIVE

The aim of the study was to analyze MR imaging features of renal epithelioid angiomyolipoma (EAML).

METHODS

This study included 17 patients with histopathologically confirmed renal EAML who underwent renal MRI scanning before radical or partial nephrectomy. MR images were retrospectively reviewed and correlated with pathological findings.

RESULT

Fifteen lesions (88.2%) appeared as round or oval. The tumor-kidney interface was round in 14 lesions (82.4%). Fifteen tumors (88.2%) presented mainly isointensity on T1WI, and eleven tumors (64.7%) presented mainly hypointensity on T2WI. Twelve lesions (70.6%) showed restricted diffusion on DWI, and the mean ADC value was 1.23 ± 0.28 × 10^-3mm²/s. Minimal fat component was identified as loss of signal intensity on opposed-phase MR images in 6 cases (35.3%). Sixteen lesions (100%) demonstrated inhomogeneous enhancement, and 7 of 16 masses (43.8%) showed reticular enhancement. Rapid wash-in and wash-out enhancement was seen in 13 masses (81.3%). In the corticomedullary phase, the mass showed markedly enhancement in 14 cases (87.5%). The irregular vessels and hemorrhage were detected in 4 cases (23.5%) and 7 cases (41.2%), respectively. One patient (5.9%) had a lymph node involvement at initial diagnosis, and showed distant metastasis after operation. In the immunohistochemical analysis, 15 tumors (88.2%) were positive for melanocytic marker (HMB45 or Melan-A), and all cases (100%) were negative for epithelial-associated markers (CK or AE1/AE3).

CONCLUSION

The presence of hypointensity on T2WI, restricted diffusion on DWI, round tumor-kidney interface, reticular, and marked enhancement (rapid wash-in and wash-out) should further raise suspicion for renal EAML. The diagnosis may be confirmed by pathological analysis.