An immunophenotypic comparison of metanephric metaplasia of Bowman capsular epithelium with metanephric adenoma, Wilms tumor, and renal development: A case report and review of the literature

Metanephric metaplasia of the parietal epithelium of the Bowman capsule is a rare pathologic finding of unknown pathogenesis that has occurred in patients with widespread malignant neoplasms of various types. We report this finding in a 25-year-old woman with partial expression of the Carney triad who died of a disseminated gastrointestinal stromal tumor, specifically a gastric stromal sarcoma. The metaplasia involved both kidneys diffusely. It originated in the parietal epithelium of the Bowman capsule, extended into the proximal tubules, and focally surrounded the glomeruli in a semicircular manner Immunohistochemical analysis revealed that the cells of metanephric metaplasia expressed the Wilms tumor gene product, bcl-2 protein, and CD57 and cytokeratin 7 and keratin AE1/AE3 focally, but not CD56. This immunophenotype parallels that of metanephric adenoma, Wilms tumor, and nephrogenic rests and overlaps with antigen expression in certain periods of renal development.