Metanephric adenoma with BRAF V600K mutation and a doubtful radiological imaging: pitfalls in the diagnostic process
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CASE REPORT
Metanephric adenoma with BRAF V600K mutation and a doubtful radiological imaging: pitfalls in the diagnostic process Niccolo Lenci1 · Pierconti Francesco1,2 · Eros Scarciglia1 · Vincenzo Fiorentino2 · Mattia Schino2 · Giuseppe Palermo1 · Marco Racioppi1,3 · Pierfrancesco Bassi1,3 · Maurizio Martini1,2 Received: 19 August 2020 / Accepted: 22 October 2020 © The Author(s) 2020
Abstract Metanephric adenoma (MA) is an uncommon benign renal tumor whose histomorphological aspect resembles that of Wilms’ tumor and papillary renal cell carcinoma. From a diagnostic and therapeutic perspective, recognition of this entity is important as it has a more favorable clinical outcome compared with Wilms’ tumor and papillary renal cell carcinoma. MA should not be treated with nephrectomy if the tumor size is small, opting for a conservative treatment. However, the preoperative diagnosis of this disease is extremely challenging. The present study describes a case of this rare disease, showing an ambiguous radiological imaging and that only after a percutaneous biopsy, was defined as a MA and treated with partial nephrectomy. Moreover, the histological diagnosis of this case was partially complicated by the equivocal immunohistochemical analysis showing negativity for BRAF VE1 staining. Only the mutational analysis demonstrated the presence of the BRAF V600K mutation (for the first time described in a case of metanephric adenoma), highlighting the necessity of sequencing in case of MA with negativity for BRAF VE1 clone. Keywords Metanephric adenoma · BRAF V600K · BRAF VE1 antibody Abbreviations MA Metanephric adenoma RCCs Renal cell carcinomas CT Computed tomograph MRI Magnetic resonance imaging DWI Diffusion-weighted imaging ADC Apparent diffusion coefficient
* Maurizio Martini [email protected] 1
Fondazione Policlinico Universitario A. Gemelli IRCCS, Università Cattolica del Sacro Cuore, Largo A. Gemelli 8, 00168 Rome, Italy
2
Divisione di Anatomia Patologica, Dipartimento di scienze della vita e sanità pubblica, Università Cattolica del Sacro Cuore A. Gemelli, Rome, Italy
3
Divisione di Urologia, Dipartimento di medicina e chirurgia traslazionale, Università Cattolica del Sacro Cuore A. Gemelli, Rome, Italy
Introduction Metanephric adenoma (MA) is a rare tumor, accounting for 0.2% of adult renal epithelial neoplasms [1]. It occurs most commonly in middle-aged women and is considered benign [2]. Radiological diagnosis of this benign tumor is typically difficult, and most MAs are misdiagnosed as renal cell carcinomas (RCCs) preoperatively. However, accurate diagnosis is of great importance as it may avoid unnecessary radical surgery, especially if the lesion has a small size [1, 3]. From a histological perspective, metanephric adenoma should be differentiated from Wilms’ tumor, oncocytoma and papillary RCC. Recently studies demonstrated that about 80–90% of MA have a BRAF V600E mutation, making this molecular alteration and the use of BRAF VE1 antibody helpful in the differential diagnos
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