The clinical and CT imaging features of metanephric adenoma

Adenoma metanéfrico: diagnóstico diferencial del carcinoma urotelial del tracto urinario superior. Reporte de un caso

Introduction: Metanephric adenoma is a rare benign kidney tumor. Patients with these tumors are usually asymptomatic, although polycythemia occurs in up 12% of cases. These masses are often described on diagnostic imaging as solid, single, well-defined, oval-shaped, unilateral lesions, located primarily in the renal medulla and without extrarenal involvement. These neoplasms are difficult to differentiate from malignant neoplasms of the upper urinary tract, so the definitive diagnosis is achieved by histopathology. Currently, the treatment of choice is radical nephrectomy. Case presentation: A 51-year-old woman from Bogotá (Colombia) was referred to the urology service of a tertiary care hospital due to bilateral lumbar pain of non-specific characteristics. At the time of consultation, the patient was asymptomatic. Renal and urinary tract ultrasound showed hydronephrosis and right renal mass. Computed tomography urography was requested, which revealed a lesion in the right renal pelvis with parenchymal invasion highly suggestive of high-risk upper urinary tract urothelial carcinoma, as well as adenopathies in the para-aortic lymph nodes. The patient underwent a radical nephroureterectomy with bladder cuff, which allowed establishing a final diagnosis of metanephric adenoma according to the histopathological study. Conclusions: Metanephric adenoma is a rare tumor that is difficult to diagnose through imaging, so it is necessary to explore additional tools to establish an accurate pre-surgical diagnosis that allows preserving the affected renal unit. Also, given their non-specificity, these tumors should be included in the differential diagnosis of lesions suggestive of upper tract urothelial carcinoma.

Imaging of Unusual Renal Tumors

PURPOSE OF REVIEW

Renal masses are a wide entity and a common finding in clinical practice. Detection of these masses has increased in the last years, yet mortality rates have slightly decreased.

RECENT FINDINGS

According to the World Health Organization classification, there are 8 types, 51 subtypes, and a lot more subsequent subclassifications of renal tumors. Histopathological analysis should always be assessed for final diagnosis of theses tumors. However, imaging can be an important diagnostic guidance. The most common diagnoses of renal tumor are clear cell carcinoma, papillary renal cell carcinoma, angiomyolipoma, and transitional cell carcinoma. Nonetheless, a considerable variety of particular tumors can arise from the kidney, challenging the expertise of radiologists and urologists on this subject. The awareness of these unusual entities is vital for professionals working at a complex medical facility with greater volume of patients. We hereby present uncommon renal tumors and its pathological and radiological features.

Metanephric adenoma with low apparent diffusion coefficient value mimicking renal cell carcinoma: A case report

RATIONALE

Metanephric adenoma (MA) is a rare and often benign tumor. Most MAs were misdiagnosed as renal cell carcinomas (RCCs) preoperatively. Diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping can help to differentiate benign and malignant tumors. However, there are still pitfalls in using DWI and ADC to discriminate benign and malignant lesions.

PATIENT CONCERNS

A 56-year-old woman had a right renal metanephric adenoma. The tumor showed very low ADC value preoperatively and was misdiagnosed as a renal cell carcinoma.

DIAGNOSIS

Intraoperative ultrasound-guided percutaneous biopsy of tumor was performed. Based on the histopathological findings and immunohistochemical stains, a diagnosis of metanephric adenoma was suggested.

INTERVENTIONS

The patient received percutaneous cryoablation of this tumor. Five years later, she underwent right partial nephrectomy because local recurrence was revealed on a follow-up computed tomography (CT).

OUTCOMES

MA was confirmed again by histological examination. The patient was uneventful after surgery.

LESSONS

ADC mapping can be used for differentiating RCCs from other benign tumors by their lower ADC values. However, some benign and malignant lesions have overlapped low ADC values. This case illustrated that a benign lesion such as MA could mimic RCC on ADC, by its highly cellular component. Cryoablation is an optional treatment, which has an increased risk of local recurrence. Follow-up CT or MRI is useful and necessary for detection of local recurrence by depicting enhancing solid parts in a tumor over time.

Imaging features of primary renal lymphoma

Background Cases of primary renal lymphoma (PRL) are quite rare and are often mistaken for renal cell carcinoma. Purpose To determine the multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) characteristics of PRL. Materials and Methods Twenty-three patients with PRL were identified by CT and MRI, and their tumor characteristics were assessed. Results Tumors exhibited single or multifocal nodules (n = 19) and diffuse renal enlargement (n = 4). Twenty-two tumors exhibited an infiltrative appearance. There was no evidence of calcification in any of the cases. Twenty-one tumors displaced or wrapped around abdominal vessels rather than encasing them. Enlarged retroperitoneal nodes were observed in three cases. Neither extension into the venous system nor distant metastasis was found. Tumor enhancement was of low attenuation compared with that of normal renal cortex and medulla ( P < 0.05). PRL was isointense on T1-weighted imaging, slightly hypointense on T2-weighted imaging and hyperintense on diffusion-weighted imaging. Twenty-two patients exhibited biopsy-confirmed PRN. There were four, 12, and seven cases of low-grade, intermediate-grade, and high-grade tumors, respectively. Patient were followed up over 16 to 166 months. Six patients died within three years and five patients died within five years. Conclusion Infiltrative appearance and tumor displacement or extension around abdominal vessels rather than vessel encasement are common findings on CT or MRI imaging and may suggest a diagnosis of PRL.

The findings of CT and MRI in patients with metanephric adenoma

Background

Metanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant tumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological examination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic resonance imaging (MRI) were retrospectively evaluated.

Methods

Eight MA patients, 17–67 years of age, were pathologically confirmed and recruited between April 2009 and November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient underwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection surgery (radical nephrectomy in five and nephron-sparing surgery in three patients).

Results

The average tumor size was 44.0 ± 23.6 mm. The lesions in 87.5 % cases were located both in the renal cortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average CT value was 37.9 ± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of MA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal parenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal parenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found in five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor was isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the renal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical experiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.

Conclusions

MA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA plays an important role in MA diagnosis and treatment.

Metanephric adenoma with diffuse calcifications: A case report

Metanephric adenoma is a rare and benign renal neoplasm originating in the epithelial cells of the kidney. The tumor has a benign course and a characteristic histopathological appearance, typically exhibiting a solid and poorly-demarcated margin with rare cystic components or calcifications. However, it is often difficult to distinguish metanephric adenoma from malignant neoplasms prior to surgical resection. To the best of our knowledge, only one case of metastasis to the lymph nodes has been described in the literature thus far. The present study retrospectively analyzed one case of surgically and pathologically-confirmed atypical metanephric adenoma. Clinical and pathological analysis, as well as computed tomography scans, revealed a mass with a clearly defined margin and diffuse calcifications. The mass was subsequently resected and the patient recovered well following the procedure.

Comparative study of CT appearances in mucinous tubular and spindle cell carcinoma and collecting duct carcinoma of the kidney

OBJECTIVE

To characterize the multidetector CT (MDCT) imaging characteristics of mucinous tubular and spindle cell carcinoma (MTSCC) and collecting duct carcinoma (CDC) of the kidney.

METHODS

21 patients with MTSCC and 18 patients with CDC were studied retrospectively. MDCT was undertaken to investigate differences in tumour characteristics.

RESULTS

Five patients with MTSCC had calcifications as did nine patients with CDC (p = 0.108). In three patients with MTSCC and four patients with CDC, the tumours had a clear boundary (p = 0.682). No patient with MTSCC had retroperitoneal lymph node metastasis as did five patients with CDC (p = 0.015). 16 patients with MTSCC showed homogeneous enhancement, whereas 11 patients with CDC showed heterogeneous enhancement (p = 0.025). The attenuation value of CDC tumours was greater than that of MTSCC and normal renal parenchyma on an unenhanced CT (p = 0.027). MTSCC and CDC tumour enhancement was less than the normal renal cortex and medulla in all phases (p < 0.001). Tumour enhancement was greater for CDC than that for MTSCC in all phases (p = 0.011, p = 0.006 and p = 0.052).

CONCLUSION

Unenhanced and dynamic MDCT may aid in diagnosis and differentiation of MTSCC and CDC of the kidney.

ADVANCES IN KNOWLEDGE

This is the first series evaluating the imaging findings of MTSCC and CDC of which we are aware, and identification of such findings may improve diagnosis of these two rare tumours.

Laparoscopic Nephron-sparing Surgery for Metanephric Adenoma in Children: A Report of 2 Cases

Metanephric adenoma (MA) is an epithelial benign tumor of the kidney and very rare in children. Here we present 2 cases of MA treated by laparoscopic nephron-sparing surgery in children. To the best of our knowledge, we report the first cases of laparoscopic nephron-sparing surgery for MA in children.

CT imaging spectrum and the histopathological features of adult metanephric adenoma

OBJECTIVE

To retrospectively evaluate the radiopathological features of adult metanephric adenoma (MA) and explore whether MA can be differentiated on CT images, including the basis of their morphological features and enhancement patterns.

METHODS

18 consecutive MA cases (age range, 18-66 years; 9 males and 9 females) were pathologically proven and recruited in our study between January 2004 and June 2014. Unenhanced and contrast-enhanced CT were performed and correlated with corresponding pathological findings to differentiate between MA and other renal tumours. The enhancement pattern, lesion contour and presence of calcifications were evaluated.

RESULTS

On unenhanced CT scan, the most common (n = 15, 83.3%) CT imaging characteristics were the presence of homogeneity and well-defined solid renal masses; the minority (n = 3, 16.7%) were heterogeneous or centrally located low-attenuation masses. Contrast-enhanced CT image revealed hypoattenuating heterogeneous masses with varying degrees of contrast enhancement in 16 (88.9%) cases, in contrast to those without increased attenuation in 2 (11.1%) cases. Scattered calcification was found only in one case (5.6%). Pathological results revealed that a total of 6 (33.3%) cases had concomitant malignant carcinoma components; 2 (11.1%) patients had malignant MA; and pure MA was found in 10 cases, with a surprisingly high proportion of malignant tumours.

CONCLUSION

The positive-predictive values of "high" enhancement seemed relatively characteristic for the diagnosis of malignant and composite MA.

ADVANCES IN KNOWLEDGE

Radiopathological features of adult MA and exploring whether MA can be differentiated on CT images, including the basis of their morphological features and enhancement patterns.