This document discusses effusion cytology, including the types and sampling of serous effusions. Serous effusions can occur in the pleural, peritoneal, and pericardial cavities and can be transudates or exudates. Transudates have little protein and few cells while exudates are rich in protein and cells. Effusions are usually sampled via thoracentesis, paracentesis, or pericardiocentesis. Normal components in effusions include mesothelial cells, histiocytes, lymphocytes, and collagen balls. Neoplastic effusions may contain malignant cells and have a more sudden onset than non-neoplastic effusions which are devoid of cancer cells.

1. EFFUSION CYTOLOGY
Nicholas Afriyie
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2. EFFUSION CYTOLOGY
• Effusion is an excess amount of serous fluid in the body cavity
• All serous membranes produces serous fluid but excess amount of the
serous fluid may indicate a pathology and is termed as an effusion.
• Serous effusion can be found in the following body cavities: pleural
cavity, peritoneal cavity and pericardial cavity.
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3. TYPES OF EFFUSION
Transudates
• ultrafiltrate of plasma with little protein and few or no cells
• arise from either increased capillary hydrostatic pressure or
decreased oncotic pressure secondary to congestive heart failure,
fluid overload, cirrhosis or hypoalbuminemia.
 Exudates
• extravascular fluid collection that is rich in protein and/or cells.
• result from increased capillary permeability or decreased
lymphatic resorption associated with infection, connective tissue
disease, pancreatitis or cancer
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4. SAMPLING TECHNIQUES
• Serous effusion is usually sampled by simply inserting a wide-bore
needle (under local anesthesia) through the body wall into the fluid-
containing cavity.
• Examples:
 Peritoneal fluid from peritoneal cavity- by paracentesis
 Pleural fluid from pleural cavity- by thoracentesis
 pericardial fluid from pericardial cavity- by pericardiocentesis
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5. GROSS APPEARANCE OF SEROUS EFFUSION
• Many serous effusions are noticeably bloodstained.
• The cancerous cells in serous effusion form a thick, whitish-yellow layer
at the bottom of container when allowed to stand and sediment
spontaneously.
• Individual particles of cancer in a serous effusion may occasionally be large
enough to be visible to the naked eye. Eg: spheroids, ellipsoids .
• Fluids containing numerous pigmented melanoma cells may be chocolate
brown.
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6. CONT’D
• Effusions containing many hemosiderophages may appear lighter brown.
• Effusions from patients who are jaundiced or that are a result of leakage of
bile into the peritoneal cavity may have a rather dark brown-orange or
greenish appearance that remains with the supernatant after the specimen
has been centrifuged
• Serous effusions caused by malignant mesothelioma of epithelial type
often have thin honey consistence due to increased viscosity of the fluid
due to the high concentration of hyaluronic acid contained in the
malignant mesothelioma.
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7. CONT’D
• Peritoneal effusion due to pseudomyxoma peritonei has heavy mucoid
consistence and the cells it contains do not sediment during
centrifugation.
•
Effusions containing numerous cholesterol crystals are
yellow and turbid and have a swirling, shimmering, gold paint
appearance when agitated
• Chylous effusions have a
milky white appearance with a creamy topmost layer due to
their high concentration of emulsified lipid.
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8. PREPARATION OF SEROUS FLUID
 Remove any clots that may be present and extract all fluid
 Pour off an aliquot (up to 50 mL) of the fluid and centrifuge for 3
mins at 2000rpm
 Pour off the supernatant
 Prepare slide with the sediment and stain
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9. Staining techniques
• Three main staining techniques are employed
a toluidine blue-stained wet film
a liquid-based preparation stained with the Papanicolaou stain
and cell blocks stained with hematoxylin and eosin
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10. NORMAL COMPONENTS OF EFFUSION
• Mesothelial Cells: Round, central nucleus with coarse chromatin.
Abundant dense cytoplasm.
• Stain:Pap stain
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11. HISTIOCYTES
Peripherally located
grooved/folded/indented/curved
nuclei
Stain: Pap stain
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12. LYMPHOCYTES
• Small cells with a single round nucleus
• Thin rim of cytoplasm.
• Stain: Pap stain
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13. COLLAGEN BALLS
• Sphere of collagen surrounded by a
single layer of mesothelial cells.
• Seen in pelvic washes, likely from
ovary.
• Benign, incidental finding
• Stain: Pap stain
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14. LYMPHOMA
• Dominated by lymphocytes
• Single disclosive cells (of varying
size depending on type)
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15. MALIGNANT MESOTHELIOMA
• All mesothelial cells (no “foreign” second
population)
Often maintain similar cytologic features (lacy
skirts, etc…)
Can be cytologically malignant or relatively bland
“More and bigger cells, in more and bigger
clusters.”
Large clusters with knobby, flower-like contours
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16. BENIGN EFFUSIONS
• Rheumatoid effusions- Granulomas, multinucleated giant cells,
and epithelioid histiocytes.
• Eosinophilic effusion- abundant eosinophils
• Lupus effusion- neutrophils with a phagocytosed nucleus, Necrotic
debris
• Chylous effusion- lymphocytes with some lipophages and mesos
• Tuberculous effusion- Abundant lymphocytes (T-cells) with sparse
mesos and
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17. Difference between Neoplastic Effusion and
Non-neoplastic Effusion
Neoplastic Effusion Non-neoplastic Effusion
The onset of neoplastic effusions may be
insidious or sudden
The onset may be slower
Neoplastic cells may be identified in fluid Devoid of neoplastic cells
Characterized by liberation of inflammatory
cytokines in response to the tumor or
damage-associated molecular patterns from
tumor or immune cells
Less inflammatory cytokines
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18. References
1. Ducatman, B. S. (2020). Cytology: Diagnostic principles and
clinical correlates. Elsevier.
2. Bibbo, M., & Hoda, R. S. (1998). Comprehensive
Cytopathology. International Journal of Gynecological
Pathology, 17(1), 93.
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