Abstract
Introduction: Metanephric adenoma (MA) is an uncommon benign tumor accounting for 0.2–0.7% of adult renal epithelial neoplasms. The clinical course is often indolent, but diagnosis should not be delayed since clinical symptoms (hematuria, fever, palpable abdominal mass, and flank pain) may be non-specific and overlap with those of a malign renal neoplasm. We report on 4 cases of AM, for which morphological and mutational analysis were performed.Material and Methods: Immunohistochemical staining was performed on sections cut from paraffin blocks to assess expression of WT1, vimentin, racemase, CK7, CD10 and RCC. Testing for the BRAF gene mutation V600 was carried out using real-time PCR (Cobas® 4800).Results: In all four cases, tumors were visible as well-circumscribed, non-encapsulated masses located in the renal cortex and extending towards the medulla. At immunohistochemical examination, tumor cells stained negative for CK7, CD10 and RCC and positive for both WT1 (nuclear, intense) and vimentin (cytoplasmic, intense, and diffuse). Molecular analysis revealed the BRAF gene mutation V600E in three cases and wild-type BRAF in the fourth.Conclusions: BRAF molecular mutation analysis may aid diagnosis in cases with atypical histological features, especially in small incisional biopsies when reassessment of surgical treatment may be considered.
Highlights
Metanephric adenoma (MA) is an uncommon benign tumor accounting for 0.2–0.7% of adult renal epithelial neoplasms
Immunohistochemical examination showed positive staining for WT1 and vimentin, and negative staining for racemase, CK7, CD10, CD57 and RCC (Figure 1B)
Positive intense staining for WT1 was recorded in the four cases reported here, but CD57 staining was in most of them weak; so, BRAF mutation helped us to confirm the diagnosis of MA
Summary
Metanephric adenoma (MA) is an uncommon benign tumor accounting for 0.2–0.7% of adult renal epithelial neoplasms. Metanephric adenoma (MA) is a rare benign tumor of the kidney, accounting for 0.2% of adult renal epithelial neoplasms [1]. Some authors have suggested that MA may derive from maturing nephroblastomas (Wilms tumor), since immunophenotypic findings overlap closely with those of differentiated nephroblastoma and nephrogenic rests [3]. Though it may occur in children, it is detected mainly in adults aged between 50 and 70 and is more common (ratio 2:1) in women [2, 4, 5]. Most authors rule out the possibility of MA becoming malignant, one case has been reported of a metanephric adenoma in association with a high-grade sarcoma (metanephric adenosarcoma) [5, 7]
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