Low power: DQ stain
Cellular smear with dual population of epithelial and stromal fragments (magenta on DQ stain)
High power: DQ stain
Dual population of epithelial and stromal fragments (magenta on DQ stain)
High power: DQ stain
Dual population of epithelial and stromal fragments (magenta on DQ stain)
Note increased cellularity in stromal fragments
Low power: Pap stain
Cellular smear with epithelial and stromal fragments and abundant naked nuclei in the background
Medium power: Pap stain
Cellular stromal fragment
Note numerous naked nuclei in background
Medium power: Pap stain
Cellular smear with ductal epithelial cells in cohesive flat sheets with naked bipolar nuclei in the background
Medium power: Pap stain
Cellular smear with dual population of epithelial and stromal fragments
High power: Pap stain
Epithelial cells with mild nuclear atypia
Medium power: Pap stain
Stromal fragment with increased cellularity and mild nuclear atypia
Features
• Dual population of epithelial and stromal cells
• Increased cellularity of stromal fragments
• Usually flat sheets of ductal cells with staghorn-like formation
• May have epithelial hyperplasia
• Ductal cells with uniform cells
• Delicate cytoplasm
• May have nuclear enlargement and atypia
• May have visible to conspicuous nucleoli
• Usually naked bipolar nuclei in background
• Cellular fibroadenomas (FA) can be difficult to differentiate from low grade phyllodes tumor. In these cases it is recommended to sign out as fibroepithelial lesion with a D/D of cellular FA vs low grade phyllodes. Usually cellular FA have less cellular stroma and less nuclear atypia than phyllodes tumor.