Low power: Pap stain
Numerous mesothelial cells, predominantly singly dispersed
Medium power: Pap stain
Numerous mesothelial cells
Note round to oval nuclei, smooth to slightly irregular nuclear membranes, small nucleoli, binucleation, and dense cytoplasm with lacy skirts
Also note windows between cells
High power: Pap stain
Mesothelial cells with round to oval nuclei, smooth to slightly irregular nuclear membranes, small nucleoli, binucleation, and dense cytoplasm with lacy skirts
Note windows between cells
High power: Pap stain
Mesothelial cells with variation in cell size but overall maintained N:C ratios
Medium power: Pap stain
Reactive mesothelial cells with round to oval nuclei, smooth to slightly irregular nuclear membranes. Note enlarged nuclei, variation in nuclear size. May have prominent nucleloli.
Features
• Mesothelial cells
– Flat sheets
– Single cells
– Small clusters
• Frequently show molding
• Cells often have windows (space between cells)
• Abundant cytoplasm with dense center (lacy skirt)
• Cell clusters can show a knobby lobulated outline
• Cytoplasmic vacuoles may be present
• Round nuclei, central or eccentric in location
• Often binucleated
• Nuclear membrane smooth to irregular (washings)
• Chromatin usually fine but may be coarse
• Small nucleoli, may be prominent when reactive
• Histiocytes
• Inflammatory cells
• May have Psammoma bodies (e.g. benign mesothelial hyperplasia)