MR imaging findings in renal medullary fibroma

A case of renomedullary interstitial cell tumor: Radiologic-pathologic correlation

Renomedullary interstitial cell tumor (RMICT), referred to as a medullary fibroma, is almost always asymptomatic and incidentally identified either at autopsy or upon resection of the kidney for other reasons. Although a few cases of RMICTs that are large in size and clinically symptomatic have been reported, there are few reports of RMICTs contrasting imaging findings with pathological findings. In this report, we describe a relatively large RMICT case of 3 cm in size, focusing on the radiologic-pathologic correlation.

Imaging Findings of a Renomedullary Interstitial Cell Tumor: A Case Report

Introduction: Renomedullary interstitial cell tumors are benign tumors of renal medulla. They are usually asymptomatic, and preoperative diagnosis based on radiological findings is challenging. Therefore, in most clinical situations, nephrectomy is ultimately performed for differential diagnosis. Case Presentation: A 54-year-old woman presented to our hospital with hematuria. An incidental mass in the left kidney was detected on abdominal computed tomography (CT) scan. The mass showed iso-attenuation to renal parenchyma in the pre-contrast image and hypo-attenuation in the portal venous phase; however, some enhancement was observed in the central portion of the mass. Based on contrast-enhanced ultrasonography (CEUS) after one year, a slight septum-like enhancement was observed in the central portion of the mass in the venous phase. In dynamic contrast-enhanced T1- and T2-weighted magnetic resonance images (MRI), the mass showed a low signal intensity, and delayed persistent enhancement was observed in 10- and 15-minute delayed phases. The mass was finally diagnosed as a renomedullary interstitial cell tumor. Conclusion: The imaging findings of renomedullary interstitial tumors included a low-signal-intensity mass of renal medulla on T1- and T2-weighted MRI and delayed enhancement on CEUS and dynamic MRI.

Benign medullary fibroma of the kidney: a rare diagnostic dilemma

Renomedullary interstitial cell tumor or medullary fibroma, is a small tumor that commonly presents as an incidental finding, but in rare cases maybe large and symptomatic. Although it is a benign tumor, it is difficult to differentiate this lesion from other malignancies of the kidney on radiological basis and hence many patients undergo radical nephrectomy. We present a case of renal medullary fibroma and various nuances associated with radiological identification of this lesion and its management related dilemmas.

Common and uncommon adult unilateral renal masses other than renal cell carcinoma

Many different masses can involve the kidney other than the commonly encountered renal cell carcinoma (RCC). The purpose of this article is to review the characteristic clinical and imaging findings of common and uncommon masses that predominantly present unilaterally in the adult patient, other than RCC. Awareness of such lesions and knowing the clinical scenario is important for appropriate diagnosis and management, especially in a multidisciplinary care setting.

Mesenchymal neoplasms of the kidney in adults: imaging spectrum with radiologic-pathologic correlation

Mesenchymal neoplasms of the kidney in adults cover a wide spectrum with characteristic ontogeny and histologic findings and variable biologic profiles and imaging findings. Benign mesenchymal renal tumors include angiomyolipoma, leiomyoma, hemangioma, lymphangioma, juxtaglomerular cell tumor, renomedullary interstitial cell tumor (medullary fibroma), lipoma, solitary fibrous tumor, and schwannoma. Malignant renal tumors of mesenchymal origin include leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, osteosarcoma, synovial sarcoma, fibrosarcoma, malignant fibrous histiocytoma, and solitary fibrous tumor. Cross-sectional imaging findings for mesenchymal renal tumors in adults are varied. Although angiomyolipomas and lipomas show macroscopic fat, lymphangiomas are cystic in appearance. Renal hemangioma may show phleboliths and a characteristic enhancement pattern. Leiomyoma typically arises from the capsule and causes buckling of the renal cortex. Although osteosarcoma may demonstrate characteristic dense ossification, most renal sarcomas demonstrate imaging features that are indistinguishable from the more common renal cell carcinoma. Although some renal mesenchymal tumors have typical imaging findings, biopsy is warranted to establish a definitive diagnosis. Awareness of the various mesenchymal renal tumors and familiarity with their imaging findings permit optimal patient management.

Computed tomography and magnetic resonance imaging features of lesions of the renal medulla and sinus

The kidneys can harbor a wide variety of lesions, many of which can be visualized by computed tomography and magnetic resonance imaging. In this article, the pertinent renal anatomic relationships as well as the histologic composition and function of the renal medulla and sinus are reviewed. Additionally, computed tomography and magnetic resonance imaging features of renal sinus and medullary lesions in adult patients are presented. This article reviews the salient imaging features of various malignant, benign neoplastic, and nonneoplastic lesions of the sinus and medulla.

MR Imaging of papillary renal neoplasms: potential application for characterization of small renal masses

The purpose of our study was to evaluate the role of MRI in demonstrating the precise nature of papillary renal tumors (P RCC) and its potential application to select patients for partial surgery. Ninety-seven tumors less than or equal to 3 cm in size [55 papillary renal cell carcinoma - 42 clear cell renal carcinoma (CC RCC)] were preoperatively evaluated by MRI. Imaging findings were assessed with a special focus on the aspect of the tumoral process. Correlations were performed with pathologic staging after surgery. At pathology, 92 tumors were established to be staged p T1 and 5 were p T3 ( 3 cases of CC RCC and 2 cases of P RCC). Ninety-four percent of papillary tumors exhibited low signal intensity with homogeneous pattern on T2-weighted images. All clear cell carcinoma were hyperintense and heterogeneous on T2-weighted sequence. Enhancement was lower and delayed in the papillary type in comparison with the clear cell type. MRI is accurate enough to predict the 'histologic' nature of papillary renal carcinoma. It is an additional argument to propose that the tumor can be removed by partial surgery.

The renal sinus: pathologic spectrum and multimodality imaging approach

Various pathologic conditions can occur in the renal sinus, primarily originating in the constituents of the renal sinus, and the renal sinus can be secondarily involved by surrounding renal parenchymal and adjacent retroperitoneal lesions. Lipomatosis and cysts are common renal sinus lesions with little clinical significance, but differentiation from other pathologic conditions is important. Renal vascular lesions such as renal artery aneurysm or arteriovenous fistula can mimic other parapelvic or peripelvic lesions at excretory urography, but their vascular nature is evident at color Doppler ultrasonography, contrast material-enhanced computed tomography (CT), and magnetic resonance (MR) imaging. Although most tumors originating in the renal pelvis are transitional cell carcinoma or squamous cell carcinoma, renal parenchymal tumors such as renal cell carcinoma or benign multilocular cystic nephroma have a tendency to grow into the renal sinus. Rare tumors of mesenchymal origin can develop in the renal sinus, but their imaging findings are nonspecific. The observation of renal sinus fat is important for detecting a small tumor located in that area and determining the exact tumor stage. Multiplanar CT or MR images can allow exact evaluation of the extent of complex renal sinus disease.

Imaging characteristics of papillary renal cell carcinoma by computed tomography scan and magnetic resonance imaging

AIM

To analyse the differences in the patterns between clear and papillary renal cell carcinomas using magnetic resonance imaging (MRI) and dual-phase helical computed tomography (CT).

METHODS

We examined seven patients with papillary renal cell carcinoma, and six with clear cell carcinoma. The highest attenuation value of tumors in the corticomedullary phase (CMP) and the excretory phase (EP) was measured using the observer-defined region of interest (ROI). MRI consisted of T1-weighted and T2-weighted spin-echo imaging.

RESULTS

All five tumors except for one with papillary renal cell carcinoma showed homogenous hypointensity, but all six tumors with clear cell carcinoma showed heterogeneous hyperintensity on their T2-weighted images. In the CMP, the mean CT numbers of the papillary renal cell carcinomas were significantly lower than those of the clear cell carcinomas. The mean enhancement of the papillary renal cell carcinomas in the CMP and the EP was significantly lower than that of the clear renal cell carcinomas. The mean CT numbers of the clear cell carcinomas in the CMP were markedly increased from those on the unenhanced CT; those in the EP were decreased gradually. But the mean CT numbers of the papillary renal cell carcinomas in the EP were still slightly more increased than those in the CMP. The enhancement patterns of the papillary renal cell carcinomas in the CMP and the EP were homogenous, but those of the clear cell carcinomas were heterogeneous.

CONCLUSIONS

We can speculate the differential diagnosis from clear to papillary renal cell carcinoma using MRI and dual-phase helical CT.

Papillary renal cell carcinoma in allograft kidney

Papillary renal cell carcinoma is a subgroup of malignant renal epithelial neoplasms. Its occurrence in allograft transplanted kidney has not been debated in the literature. We report two pathologically proven cases and discuss the clinical hypothesis for such neoplasms and the aspect on MR images. The paramagnetic effect of the iron associated with an absence of signal coming from calcifications is a plausible explanation for this unusual hypo-intense appearance on T2-weighted sequence.

Small renal cell carcinoma: MRI with pathologic correlation

The MRI features of small renal cell carcinomas (RCCs) were retrospectively reviewed and correlated with histology in 24 patients. MRI features on both T1- and T2-weighted images were classified into hypointensity, isointensity, and hyperintensity. Each tumor was pathologically classified into four types: alveolar, papillary, tubular, and cystic. These findings were correlated with MR signal intensities. Alveolar tumors showed hypointensity to isointensity on T1-weighted image and isointensity to hyperintensity on T2-weighted image. In contrast, all papillary tumors showed hypointensity on T2-weighted image. Four of six tumors with hypointensity on T2-weighted image were caused by hemosiderin deposition, hemorrhage, and necrosis. However, there were two papillary RCCs that showed hypointensity on T2-weighted image despite no hemosiderin deposition and no hemorrhage. We conclude that papillary RCC is associated with T2-hypointense appearance as well as hemosiderin deposition, hemorrhage, and necrosis.

Renal medullary fibroma: a case report and review

A case of renal medullary fibroma in a woman is presented. A CT scan, which was performed for examination of cholelithiasis, incidentally revealed a mass in the left renal pelvis, and retrograde pyelography showed a filling defect in the same site. Left nephrectomy was performed. Histological examination revealed a renal medullary fibroma. The diagnostic and therapeutic dilemmas associated with this condition are discussed.

Benign renal tumors: diagnosis and treatment

Renal tumors both benign and malignant have two basic growth patterns. One pattern is that of appositional growth in which a round mass is shown displacing the normal kidney. The other is that of infiltrative growth. In this situation, the tumor cells grow between the scaffolding of the normal glomerulae and tubules. Thus, in this situation, kidney function appears normal until late in the disease. The kidney thus keeps its reniform shape but does increase in size (bean or orange to grapefruit pattern).