W2L4 - Serous Effusions

Question 1

Sensitivity and Specificity of Serous Effusions

Answer 1

Sensitivity of 58%

Specificity of 97%

Question 2

Serous Effusion - Sampling Methods

Answer 2

Serous effusions can be removed at the time of surgery or when a serous cavity causes discomfort to the patient
- due to excessive build up of fluid
Done by needle into cavity under anaesthetic
Peritoneal fluid - abdominal paracentesis
Pleural fluid - thoracentesis
Pericardial fluid - pericardiocentesis

Question 3

Collection of Serous Effusions

Answer 3

Fluid is collected into a clean, sterile, dry container which is sent to a laboratory ASAP
Formalin or alcohol must NOT be added as this prevents the cells from adhering to the slide but also interferes with the quality of staining by the Papanicolaou method

Question 4

What is an Effusion

Answer 4

Accumulation of serous fluid above the normal amount is considered an effusion

Question 5

Transudates

Answer 5

Transudates are characterised by:
- low protein content < 30g/L
- low specific gravity < 1.015
- low cellular yield
- low fibrin content
The smears usually consists of mesothelial cells, macrophages and occasional lymphocyte or neutrophils

Question 6

Exudates

Answer 6

Exudates occur due to damage of the capillary walls within the serosal connective tissue

• high protein content >30g/L
• high specific gravity > 1.015
• high cellularity (increased inflammatory cells caused by inflammation, or malignancy).

Question 7

Normal Cells

Answer 7

All pleural, peritoneal (ascitic) and pericardial fluids contain cells:
- mesothelial cells
- macrophages
- red blood cells
- neutrophil
- eosinophils
- lymphocytes
- megakaryocytes
Other cells may included;
- ciliated cells from respiratory tract (if lung is punctured)
- hepatocytes (seen in right sided effusions)

Question 8

Mesothelial Cells - Hypertrophy and Hyperplasia

Answer 8

Mesothelial cells undergo a wide range of hypertrophy and hyperplasia due to a wide range of stimuli
- inflammation
- necrosis of underlying parenchyma
- presence of foreign substance within the cavity (blood, air)
The presence of effusion will result in proliferation of mesothelial cells

Question 9

Mesothelial Cells - Cytology

Answer 9

Mesothelial cells exfoliating into a serous fluid are:

• round
• round nuclei
• cytoplasm dense and stains grey/green with Pap
• cytoplasm less dense at periphery
• well defined cell membrane
• chromatin uniformly granular
• nucleoli
• may be multinucleated
• vacuolation
• form ‘windows’ when touching other mesothelial cells

Question 10

Vacuoles Seen in Mesothelial Cells

Answer 10

Can have:

• one or two unobtrusive vacuoles scattered throughout the cytoplasm but more likely near the nucleus
• a large solitary vacuole that displaces the nucleus to the periphery of the cell
• an elongated perinuclear vacuole which appears to curve around the nuclear membrane

Question 11

Mesothelial Cell Cytology - Sheets and Groups

Answer 11

Small mesothelial cell clusters are common
Often in peritoneal (ascitic) effusions, larger sheets of flat mesothelial cells are present > 10 cells/sheet.
Mesothelial cells can appear to wrap around each other

Question 12

Reactive Mesothelial Proliferation

Answer 12

Reactive mesothelial cells are commonly seen in association with recent surgery
Increased clusters of mesothelial cells
Variable anisokaryosis including multinucleation and binucleation
Slightly enlarged nuclei with prominent/sometimes multiple nucleoli
Smooth nuclear membranes, smaller clusters have ‘windows’

Question 13

Mesothelial Cell Difficulties

Answer 13

Degenerate - vacuoles may be present and may mimic adenocarcinoma
Multinucleation
Mitoses
When they contain ingested material e.g. pigment
Atypical - especially in long standing effusions, pericardial effusions and inflammatory lesions
In practice, ALL effusions with a reactive mesothelial proliferation should have an EMA performed

Question 14

Neutrophil - Empyema

Answer 14

Most effusion specimens will contain certain number of neutrophils
Number varies from the occasional neutrophil to a purulent effusion
Purulent effusions are macroscopically light yellow in colour with a turbid/creamy appearance
If an infection is suspected they may be malodorous
Inflammation, infarction or rupture of an organ are the principal causes of serous effusions containing numerous neutrophils
Empyema develops as a complication of pneumonia, however can develop as an extension of an adjacent abscess, subdiaphragmatic, paravertebral or lung

Question 15

Macrophages

Answer 15

Macrophages are commonly identified in serous effusions
They are easily identified due to:
- eccentric round/oval/bean shaped nuclei
- fine, delicate, lacy cytoplasm
- cytoplasm may contain leukocytes, red blood cells, carbon particles, lipid droplets, nuclear particles, melanin or haemosiderin

Question 16

Lymphoid Cells

Answer 16

Most are small mature lymphocytes in type
T and B cells cannot be differentiated on cytology alone but can be identified by immunocytochemical staining using monoclonal antibodies
Most lymphoid cells in a benign effusions are of T cell origin
Appear round with deeply stained nuclei
Size vary according to the amount of air drying that may occur
Minimal rim of basophilic cytoplasm on Papanicolaou staining

Question 17

Non-Specific Effusion

Answer 17

Nearly all inflammatory serous effusions are non specific, they do not reveal the aetiologic background
Examples:
1. Acute purulent inflammation - contains numerous numbers of neutrophils
- macroscopically appear thick yellow/creamy consistency
- most pleural empyema are 2º to 1º bacterial pneumonia
2. Chronic inflammation - which is a predominance of lymphoid cells
- most common underlying cause is neoplasms in the lung
- next most common cause is tuberculosis
- need to exclude chronic lymphocytic lymphomas/leukaemias

Question 18

Specific Inflammatory Effusions - Rheumatoid Disease

Answer 18

Necrotising granulomatous inflammation found in the synovium and subsynovial tissue of rheumatoid arthritic joints
Features seen on cytology effusions are pathognomic:
- elongated spindle shaped macrophages
- cytoplasm is moderately dense, acidophilic or cyanophilic and finely granular ground glass appearance
- multinucleated giant macrophages - round to oval nuclei with > 20 nuclei
- necrotic granular background formed by necrosis and disintegration of the macrophages
- may contain cholesterol crystals

Question 19

Specific Inflammatory Effusions - Systemic Lupus Erythematosus

Answer 19

The LE cell: a neutrophil or a macrophage that has engulfed the denatured nucleus of injured cells
The injury is caused by circulating antinuclear antibodies present in excessive amounts in the serum of patients with SLE
LE cells contain engulfed haematoxylin bodies in Papanicolaou smears
In LE cells the nucleus is pushed over to the side and may seem to be a continuous crescent shaped band

Question 20

Pneumothorax

Answer 20

Frequently accompanied by an effusion, induced by the presence of air and its impurities into the pleural cavity and pulmonary parenchyma
Cytology picture is non specific but may contain increased numbers of eosinophils due to allergenic impurities
The presence of air may also stimulate mesothelial cells to enlarge leading to hypertrophy the mesothelial cells

Question 21

Tuberculosis

Answer 21

TB is often accompanied by a predominance of lymphocytes within the effusion sample
Only isolated mesothelial cells are identified, this is due to increase amount of fibrin deposit on the pleural surface
May also seen multinucleated giant cells and epithelioid histiocytes that form granulomas

Question 22

Endometriosis

Answer 22

An extrauterine growth of functioning endometrial tissue
Commonly encountered in pelvic washings/ascitic fluids
Not common in the pleura, however can occur
Fluid macroscopically appears chocolate brown in colour
Cytology contains small columnar shaped cells, hemosiderin laden macrophages, may see endometriotic fragments of tissue, with both stromal and epithelial component