A composite renal tumor: metanephric adenofibroma, Wilms tumor, and renal cell carcinoma: a missing link?

Paediatric metanephric tumours: a clinicopathological and molecular characterisation

To characterize metanephric tumours in children, we performed a literature review investigating paediatric metanephric adenomas (MA), metanephric stromal tumours (MST) and metanephric adenofibromas (MAF). Including two patients from our own institution (MA, MAF), 110 individual cases (41 MA, 20 MAF, 49 MST) were identified. Additionally, fifteen composite tumours were identified, with areas of MA/MAF and Wilms tumour (WT) or papillary carcinoma. No distinct clinical or radiological features could be defined. In pure metanephric tumours, histologically proven distant metastases were reported once (MA), relapse was reported once (MST) and one tumour-related death occurred (MST). Somatic BRAF-V600E mutations were tested in 15 cases, and identified in 3/6 MA, 3/3 MAF, and 6/6 MST. In our institution the MA harboured a somatic KRAS-G12R mutation. Overall, paediatric metanephric tumours are difficult to discriminate from other renal tumours at presentation, behave relatively benign, and the occurrence of composite tumours warrants analysis of underlying (genetic) pathways.

Metanephric Adenofibroma Masquerading as Wilms' Tumor

Metanephric adenofibroma is a rare, biphasic, benign tumor containing both stromal and epithelial components and could be potentially mistaken as Wilms’ tumor (WT). We present a 5-year-old girl who was suspected to have metastatic Wilms’ tumor on radiological investigations/tru-cut biopsy and had received neoadjuvant chemotherapy, but postoperatively final histopathology revealed it as metanephric adenofibroma. No postoperative chemotherapy was given

Minimal fat renal angiomyolipoma with lymph node involvement: A case report and literature review

Renal angiomyolipomas (AML), consisting of fatty tissue, blood vessels, and smooth muscular cells in various proportions, is a relatively common benign renal neoplasm. Simultaneous involvement of the kidney and lymph nodes is uncommon and might be confused with an advanced renal cancer. AML is divided into minimal fat AML and fat-predominant AML. However, minimal fat AML with lymph node involvement is extremely rare and difficult to differentiate from RCC on images. We report such a case and review the literature.

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.

Congenital renal tumor: metanephric adenoma, nephrogenic rest, or malignancy?

We report a renal tumor detected by prenatal ultrasound and resected at 2 months of age. This 9-cm, solid mass was composed of tubular and papillary structures lined by small, uniform epithelial cells. There was local invasion into renal parenchyma and a tumor deposit in a hilar lymph node. The tumor was immunopositive for WT1, pankeratin, and CD10; focally positive for CK7; and negative for EMA and TFE3. Based on morphology and immunophenotype, the favored diagnosis was metanephric adenoma over Wilms tumor, renal cell carcinoma, and nephrogenic rest. However, metanephric adenoma only occasionally occurs in children and has never been reported prenatally. Alternatively, this tumor might be a congenital Wilms tumor that differentiated completely. Although the nature of the tumor remains unconfirmed, resection appears to have been curative; the patient remains disease-free 18 months following surgery alone.

Adult metanephric adenoma presumed to be all benign? A clinical perspective

Background

In most documented literature, metanephric adenoma (MA) is described as a benign tumour. Nevertheless, the nature of MA remains unclear and the clinical criteria of different MA subtypes are not well established. In the present study, we investigated the clinicopathological characteristics of MA, especially those of the uncommon histological subtypes.

Methods

A cohort study was performed on 18 patients with pathologically proven MA in our institute from January 2004 to June 2014. The patients’ clinicopathological and radiological data were retrospectively analysed and evaluated with an emphasis on the corresponding subtypes.

Results

The patient population had a female: male ratio of 1:1 and mean age of 50 years (range, 18–66 years). The mean tumour size was 3.9 cm (range, 1.4–9.0 cm). There were no pathognomonic radiological features that posed a challenge for a preoperative diagnosis of MA. Fourteen patients underwent radical nephrectomy, and the other four underwent partial nephrectomy. Three histological subtypes were observed: classic MA (n = 10), malignant MA (n = 2), and composite MA with coexistence of different malignant components (n = 6). Despite the presence of atypical histological features and malignant components among the patients, only one patient developed distant metastasis (median postoperative follow-up, 56 months; range, 30–86 months).

Conclusions

MAs are a heterogeneous group of neoplasms with different biological characteristics. The correct identification of this entity and its subtypes would facilitate stratification of optimal management protocols and accurate assessment of the prognosis.

BRAF mutations in pediatric metanephric tumors

Metanephric neoplasms of the kidney are uncommon, and some cases are associated with papillary carcinoma. Most cases of metanephric adenoma occur in adults, with fewer than 25 cases reported in children, and metanephric adenofibroma is even less common. The few metanephric tumors studied at the genetic level have not shown the gains of chromosomes 7 and 17 commonly seen in renal cell carcinoma, suggesting that the carcinoma arising in this setting has a separate genetic origin from the adenoma. However, the assumption that this carcinoma has the same chromosome gains as sporadic renal cell carcinoma has never been validated. We studied 4 cases of metanephric tumors in children, including 1 metanephric adenofibroma with papillary carcinoma. The composite tumor was studied by single nucleotide polymorphism array and fluorescence in situ hybridization, with the adenoma and carcinoma components analyzed separately. No copy number alterations were detected in either component. A BRAF V600E mutation has been reported in most cases of metanephric adenoma in adults. We performed BRAF V600E immunostaining and sequencing in our 4 pediatric cases. Three cases had a BRAF V600E mutation including the composite tumor, with both the adenoma and carcinoma components showing the same mutation. This finding provides the first genetic evidence that these 2 tumors are biologically linked. Ten cases each of pediatric renal cell carcinoma and Wilms tumor were immunonegative. Thus, BRAF V600E immunostaining is a helpful marker for pediatric metanephric adenoma, and additional research is required on the possible role of this mutation in the development of renal carcinoma.

Composite tumor of metanephric adenoma and Wilms' tumor of the kidney: A case report and review of the literature

Metanephric adenoma (MA) and Wilms' tumor (WT) are two distinct types of renal tumors. Composite MA and WT of the kidney are extremely rare. Here, a rare case of composite MA and WT of the kidney in a 36-year-old male is described. MA and WT each have their own histopathological features, respectively, and they focally share morphological similarities, which can be a diagnostic challenge. Immunohistochemistry is useful in the differential diagnosis of MA and WT. The histopathological features and differential diagnosis of the composite tumor are emphasized here to promote a better and broader understanding of this less understood subject.