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Papillary Renal Cell Carcinoma

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  • 2nd most common type of renal carcinoma, divided into 2 types (types 1 or basophilic and 2 or eosinophilic).
  • Has higher tendency for multifocality and bilaterality than other RCC.
  • Cytogenetics: +7, +17 and -Y
  • Gross: well circumscribed, with pseudocapsule and variegated (yellow-tan from histiocytes and dark brown from hemorrhages) and occasionally multifocal (helpful gross features) (image A).
  • Histology:
    • Characterized by papillae with central fibrovascular core (true papillae) containing foamy histiocytes lined by single layer of cells (image B).
    • Tumor cells have either basophilic cytoplasm (type 1) (image C) or abundant eosinophilic (type 2) cytoplasm (image D).
    • Nuclei are round, small, with low-grade appearance.
    • ~1/2 of tumors may have solid (non-papillary) growth consisting of tubules and "glomeruloid" growth.
    • May have psammoma calcifications.

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  • Immunohistochemistry: CK7+ and AMACR+.
  • Behavior is better than clear cell RCC but worse than chromophobe RCC.
  • DDX:
    • Metanephric adenoma: primitive appearing blue cells, WT1+.
    • Mucinous tubular and spindle cell carcinoma: may look like papillary RCC with sarcomatoid change because of the spindle cells; but contains extracellular mucin and spindle cells are low-grade.
    • Other RCC with substantial papillary growth such as:
      • Collecting duct carcinoma: associated with high-grade invasive glands (adenocarcinoma) and desmoplasia and AMACR-.
      • Translocation-associated carcinomas: with clear cells and "voluminous" cytoplasm, TFE3+.
      • Clear cell papillary RCC: with clear cells, CAIX+.