Affiliation:
1. From the Departments of Pathology, Northwestern Memorial Hospital, Northwestern University Medical School, Chicago, Ill (Dr Pins); Vancouver Hospital and Health Sciences Centre, Vancouver, British Columbia, Canada (Dr Jones); Juan Canalejo Hospital, La Coruna, Spain (Dr Martul); Mount Auburn Hospital, Cambridge, Mass (Drs Kamat and Umlas); and Baptist Hospital of Miami (Fla) (Dr Renshaw).
Abstract
Abstract
Background.—Metanephric adenoma is a very rare benign renal tumor; only 80 well-documented cases have been reported to date. We have seen several renal tumors that were originally incorrectly diagnosed as metanephric adenoma.
Design.—We present 3 unusual renal tumors (2 primary and 1 metastatic), each of which illustrates important pathologic features useful in discriminating metanephric adenoma from malignant mimics.
Results.—Case 1 involved a 46-year-old man with multiple small, cortical, solid, papillary (chromophil) renal cell carcinomas in his right kidney; the patient developed multiple, histologically identical, solid, papillary (chromophil) carcinomas in the opposite kidney 17 months later. Case 2 involved a 32-year-old woman with a 14-cm right renal tumor who developed soft tissue and bone metastases over a 17-year period. Case 3 involved a 52-year-old woman who presented with a 1.8-cm corticomedullary renal nodule, which eventually proved to represent a metastasis from a poorly differentiated (insular) carcinoma of the thyroid. All 3 tumors superficially resembled metanephric adenoma and consisted of primitive, dark-staining cells arranged in tubules or sheets. Each tumor, however, also had features inconsistent with the diagnosis of metanephric adenoma, including multifocal lesions with a variable nuclear-cytoplasmic ratio and diffuse cytokeratin 7 and epithelial membrane antigen immunopositivity in case 1, a 14-cm-diameter tumor with occasional mitoses in case 2, and a distinct fibrous capsule with capsular and vascular invasion in case 3. In addition, all 3 tumors lacked the cytologic features of bland overlapping nuclei with imperceptible cytoplasm consistently seen in metanephric adenoma.
Conclusion.—Adherence to strict histopathologic criteria will discourage misdiagnosis of a malignant or potentially malignant renal neoplasm as the rare and always benign metanephric adenoma.
Publisher
Archives of Pathology and Laboratory Medicine
Subject
Medical Laboratory Technology,General Medicine,Pathology and Forensic Medicine
Cited by
46 articles.
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