Medium power: Pap stain
Cellular fragment with nuclear enlargement, irregularity, and crowding with conspicuous to prominent nucleoli
Low power: DQ stain
Stromal fragment (magenta on DQ stain) with increased cellularity
High power: DQ stain
Cellular stromal fragment with nuclear crowding and atypia
High power: DQ stain
Stromal cell atypia with enlarged nuclei, pale cytoplasm and cytoplasmic vacuolation
Medium power: Pap stain
Dual population of epithelial and stromal cells
Note single intact stromal cells in the background
High power: Pap stain
Cellular stromal fragment with nuclear enlargement and irregularity, conspicuous to prominent nucleoli, and pale vacuolated cytoplasm
Features
• Dual population of epithelial and stromal cells
• Cellular stromal fragments
• Single intact stromal cells
• Bland to atypical stromal cells
• Pale cytoplasm
• May have intracytoplasmic vacuoles
• Spindle shaped nuclei
• May have nuclear enlargement, irregularity
• May have multiple nucleoli
• May have mitosis and necrosis
• May have hemorrhage and cystic degeneration
• Low grade phyllodes tumor can be difficult to differentiate from cellular fibroadenomas (FA). In these cases it is recommended to sign out as fibroepithelial lesion with a D/D of low grade phyllodes vs cellular FA. Large tumor with rapid growth, older age, marked stromal cellularity, and single atypical stromal cells, favor phyllodes tumor.
• Express CD34, vimentin, may express SMA, CD117, BCL-2
Simi U et al. Acta Cytol. 1988 Jan-Feb;32(1):63-6.