Metanephric Adenoma with cystic changes- An uncommon presentation of a rare tumor in a young adult

ABSTRACT

Metanephric adenoma (MA) is a rare benign neoplasm of the kidney that is usually asymptomatic and incidentally diagnosed. MA usually present as a solid mass; however, a cystic presentation has been reported. The main differential diagnosis of MA is the epithelial predominant Wilms tumor (e-WT) and the solid variant of papillary renal cell carcinoma (pRCC). The presence of the BRAF gene mutation has recently been reported in 85% of MA, and less than 10% of cases of MA do not express this specific gene mutation. Herein we report a 22-year-old man who presented with back pain and abdominal discomfort with a renal mass on the computed tomographic scan. The diagnosis of metanephric adenoma was confirmed histopathologically. In our case, the tumor presented as a solid and cystic mass hence mimicking a papillary renal cell carcinoma. The VE1 protein, which correlates with BRAF gene mutation, did not show any significant expression. We want to highlight that MA can present as a cystic lesion that should be taken into account to avoid unnecessary radical nephrectomy. Also, we demonstrated that a subset of MA might not harbor the BRAF gene and, they are classified as the BRAF wild type MA.