W4L5 - Malignant Mesothelioma

Question 1

Asbestos

Answer 1

General term
Inorganic silicate minerals characterised by:
- long thin separable fibres
- high tensile strength
- flexibility
Found in:
- thermal/acoustic insulation
- corrosive chemical resistance
- woven into fabrics
- stabiliser for air conditioning products and sealers

Question 2

Types of Asbestos - Serpentine Family

Answer 2

Chrysotile (white) - most commonly used and often contaminated with tremolite
Fine texture, high flexibility and good heat resistance.
Used in cement, brake pads/linings, roofing

Question 3

Types of Asbestos - Amphiboles Family (Commercial)

Answer 3

Crocidolite (blue)
- v. thin fibres, strong and heat resistant
- v. brittle and most harmful
Amosite (brown)
- mostly in Africa
- strong heat resistant
- used in cement sheets, plumbing, insulation and electrical insulation

Question 4

Types of Asbestos - Amphiboles Family (Non-Commercial)

Answer 4

Anthophyllite
- found as a contaminant in composite flooring
- used in talc and talcum powder
Tremolite
- found in paints, sealants, asbestos containing insulation products, talc.
Actinolite
- brittle
- found in paints, sealants and drywall
- expands when heated making it an effective insulation material for fire proofing

Question 5

Causes of MM

Answer 5

Asbestos

Erionite

Question 6

Asbestos Fibre Potency

Answer 6

Crocidolite > amosite > tremolite > chrysotile
Chrysotile rarely if ever causes MM
Chrysotile mixed with amphiboles
Risk of disease related to intensity and type of exposure and time since exposure

Question 7

Common Asbestos Related Diseases

Answer 7

Pleural Fibrosis
Pleural Plaques
Asbestosis
Recurrent pleural effusion
Lung Cancer
Malignant mesothelioma
Associated with neoplasms in other organs including kidney, stomach

Question 8

How do Fibres cause MM

Answer 8

Pleural irritation
Chromosome damage/mutation
Cytotoxic radicals
Oncogene (e.g. cell proliferation switches) activation

Question 9

MM Histological Subtypes

Answer 9

Epithelioid MM: 40-60%
Biphasic MM: 30-40%
Sarcomatoid MM: 10-20%

Question 10

Diagnosis of Mesothelioma

Answer 10

Two step approach

1. Separating malignant mesothelioma from reactive mesothelial cell proliferation
2. Separating malignant mesothelioma from a secondary adenocarcinoma

Question 11

Cytology of MM

Answer 11

Low power appearance demonstrates abundant cell aggregates usually large with up to >50-200 cells in 3D aggregates
Nuclear atypia
Cellular enlargement – more pronounced in malignant mesothelial cells than benign cells
Macronucleoli
Evidence of cohesive papillary like fragments forming spheres with smooth contours or mulberry like aggregation
Sometimes windows between cells
Orangeophilic extracellular matrix cores or collagen cores sometimes seen in aggregates
Sometimes proteinaceous material in background (hyaluronic acid)
Evidence of cytoplasmic blebbing or protrusions
Absence of a foreign cell population

Question 12

What is a Metastatic Mesothelioma

Answer 12

Occurs when malignant cells spread from the primary tumor, in the lining of the lungs or abdomen, to other parts of the body