Low power: Pap stain
Cystic background consisting of foamy proteinaceous fluid
Low power: DQ stain
Cystic background with foamy proteinaceous fluid
High power: DQ stain
Histiocytes/foam cells in a foamy proteinaceous fluid background
Low power: Pap stain
Benign ductal cells and histiocytes/foam cells in a foamy proteinaceous fluid background
Note: Ductal cells may show lactational changes (reactive atypia with prominent nucleoli and vacuolated cytoplasm)
Look for history of pregnancy/lactation
Features
• Rare benign ductal epithelial cells
• Histiocytes/ foam cells
• Also known as milk retention cyst
• Caused by lactiferous duct occlusion
• Usually history of pregnancy/ lactation
• Fluid grossly milky
• May have lactational change
• May have vacuolated cytoplasm
• Typically benign-appearing
• May have reactive atypia
– Enlarged nuclei
– Prominent nucleoli
• Foamy consisting of lipid and protein
Novotny DB et al. Acta Cytol. 1991 Nov-Dec;35(6):676-86.