Key features

•  Aggressive course
•  High rate of axillary lymph node metastasis (66–100%)
•  Morphology– tubulealveolar, morular clusters (spongelike), micropapillary
•  Frequent calcifications, including psammoma bodies (42–67%)
•  EMA (epithelial membrane antigen) has reverse membrane staining (outer border of cells)
•  Receptor status
  • ER: 62–91% +
  • PR: 46–72% +
  • HER-2: 36-81% +
    • HER-2 FISH amplified tumors may have 1+ (negative) or 2+ (equivocal) staining by IHC, and it is recommended that IHC and FISH be used in cases with micropapillary pattern.