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The immunohistochemical profile of metanephric adenomas (MA) is as follows:
- POSITIVE: WT1 (strong, nuclear), PAX8 (strong, nuclear), CD57 (cytoplasmic/membranous)
- NEGATIVE: CK7 (may be weak, patchy +), AMACR
The combination of CK7-, AMACR-, CD57+ and WT1+ is considered characteristic of metanephric adenoma. Strong diffuse positivity for CK7 and AMACR argues against the diagnosis of MA and favors papillary renal cell carcinoma in the appropriate morphologic context.