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1:
Metanephric Adenoma in Needle Biopsy
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Comments: Metanephric adenoma is a unique renal tumor with benign biologic behavior in spite of their large size. It may be associated with polycythemia. There is female predominance. This needle core biopsy shows tightly packed small tubules with little intervening stroma. Given the benign nature of the tumor, this elderly patient with compromised renal function opted not to undergo nephrectomy.
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3:
Metanephric Adenoma : Well-circumscribed borders
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Comments: The majority of the tumors are well-circumscribed as seen in the previous and this image. They are usually not encapsulated but may have a thin and discontinuous pseudocapsule. The areas that bulge above the kidney are separated from the perirenal tissue by renal capsule.
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4:
Metanephric Adenoma
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Comments: The tumor is composed of small, uniform, round acini and tubular structures separated by scant stroma. The lining epithelial cells are uniform with hyperchromatic nuclei and have scant cytoplasm.
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5:
Metanephric Adenoma
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Comments: Tight packaging of small acini creates a near-solid appearance. There is no cytologic atypia. Mitotic figures are rare.
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6:
Metanephric Adenoma : Glomeruloid structures
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Comments: More than 50% of cases contain papillary structures, consisting of minute cysts into which small blunt papillary structures protrude. Many such structures resemble immature glomeruli. Usually there are no blood vessels in these papillary structures.
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7:
Metanephric Adenoma : Psammoma bodies
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Comments: Psammoma bodies are commonly seen in Metanephric Adenomas. References: 1) Am J Surg Pathol 19(6): 615-626, 1995. 2) Am J Surg Pathol 19(10): 1101-1114, 1995.
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