Table 1:

Blood-derived constituents of effusions.

Cells	Diff-Quik stain	Papanicolaou stain
Red blood cells	Eosinophilic, anucleated, round, with central pallor	Eosinophilic
		Biconcave disks
		Anucleated
Neutrophils	Nucleus: basophilic, multilobed with 2–5 lobes	Nucleus: basophilic, multilobed with 2–5 lobes
	Cytoplasm: faintly eosinophilic with fine granularity	Cytoplasm: faintly cyanophilic, granular
Eosinophils	Nucleus: basophilic, bilobed (may have up to four lobes)	Nucleus: basophilic, bilobed (may have up to four lobes)
	Cytoplasm: numerous, coarse, eosinophilic granules	Cytoplasm: light pink to light green with coarse granularity
Basophils	Nucleus: central, rounded to irregularly shaped	Nucleus: central, rounded to irregularly shaped Cytoplasm: coarsely granular, light pink to light green
	Cytoplasm: coarse, basophilic granules which may overlap the nucleus
Histiocytes	Nucleus: reniform (kidney or bean shaped), central to eccentric	Nucleus: reniform (kidney or bean shaped), central to eccentric
	Cytoplasm: vacuolated, foamy, without distinct ectoendoplasmic staining pattern, and without peripheral cytoplasmic blebs. Hemosiderin appear as gray to blue granular material in Diff Quik stained preparations	Cytoplasm: foamy, may contain phagocytosed material such as hemosiderin pigment, which appear as yellow to brown granular material in Pap stained preparations.
Megakaryocytes	Morphology similar to that in bone marrow smears Nucleus: large, multilobed nuclei Multilobation may not be distinct in all cells Cytoplasm: variable amount	Large, multilobed nuclei Cytoplasm: variable amount. Megakaryocytes with high N/C ratio may be misinterpreted as neoplastic or viral cytopathic effect, especially in PAP-stained preparations