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

Atypical metanephric adenoma: Shares similar histopathological features and molecular changes of metanephric adenoma and epithelial-predominant Wilms’ tumor

Background

Metanephric adenomas (MAs) are rare, benign renal tumors. Wilms’ tumors (WTs) are malignant embryonic tumors that originated from nephrogenic blastemal cells. However, some tumors have similar morphology to both MA and epithelial-predominant WT, which makes differential diagnosis difficult. We aimed to analyze the morphological, immunophenotypic and molecular changes in overlapping cases to explore their attribution.

Methods and results

Twenty MAs, ten WTs, and nine cases with MA/WT overlapping histological features were studied. Twenty tumors demonstrated the typical morphological spectrum of MA with high cellularity and were composed of tightly packed small, uniform, round acini with a lower Ki67 index. Almost all MAs (94.7%, 18/19) were detected with BRAF V600E mutation. The ten WTs were epithelial-predominant WTs with glands, rosettes and glomerular structures, which also showed a higher Ki-67 index (up to 60%), invasive growth patterns, and a lack of BRAF mutation. However, the other nine overlapping cases showed two components: typical MA-like areas and epithelial WT-like areas. The cells of the WT-like areas were tubular, columnar and showed marked cytological atypia, with a Ki-67 proliferative index of up to 30%. The immunophenotype of these overlapping lesions was not significantly different from that of typical MA and they positively expressed WT1 and CD57. The BRAF V600E mutation was detected in both WT-like and MA-like areas in nine overlapping tumors. The follow-up data of 31 patients were analyzed, with a median follow-up time of 66 months (range, 8-45 months). Even though most patients with WT underwent radiotherapy or chemotherapy after surgery, two died, and one had liver metastasis. No MA or overlapping cases showed any evidence of recurrence or metastasis after surgery.

Conclusions

The molecular changes in tumors with overlapping morphological features were the same as those of typical MA; thus, we think that these tumors should be classified as MA and further called atypical MA. It is important to note that atypical MA is not a neglected subtype of MA. It possesses different histological morphology and a higher Ki-67 index but has the common imaging characteristics, immunophenotype and gene expression as typical MA, and patients usually have a good prognosis.

Standard of care for adult Wilms tumor? From adult urologist to pediatric oncologist. A retrospective review

Nephroblastoma or Wilms tumor, a common embryonal tumor in children, can occasionally occur in adults. The survival of patients older than 18 years is reported to be significantly inferior to that of pediatric patients. Establishing a diagnosis for these rare tumors can be challenging for both clinicians and pathologists, who are not accustomed to considering Wilms tumor as a potential differential in adults. This leads to misdiagnosis and a subsequent delay in the initiation of appropriate therapy. The standard of care is not well established for Wilms tumors in adults. We provide here a comprehensive review of the international literature on the subject with the current management protocols in France. We also propose the need of strong inter-disciplinary collaboration between surgeons, pathologists, and medical and pediatric oncologists for increasing knowledge and formulating treatment strategies for these rare tumors. Homogenous guidelines for treating adults with Wilms tumors have been proposed for all patients in France.

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.

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.