Laboratory Diagnostic Investigations (I) - Anatomical pathology

Question 1

Purpose of a Coroner autopsy?

Answer 1

Coroner decides necessity

Inquire into cause and circumstance of death without valid evidence for cause of death

Question 2

14 criteria for reportable deaths

Answer 2

Uncertain 
Unattended (14days)
Accident 
Crime 
Anesthetics (<24h)
Operations (within 48h)
Occupational-related
Stillbirths 
Maternal death 
Sepsis (unknown orign)
Suicide 
In custody (nursing home, mental hospital) and neglected 
Homicide 
Deaths outside HK

Question 3

Purpose of Clinical autopsy

Answer 3

Full or limited autopsy to confirm unexplained clinical findings that may or may not contribute to cause of death

Need consent from next-of-kin

Question 4

Preparation of patient sample from autopsy?

Answer 4

• Tissue Fixation in 10% buffered Formalin

- Paired tumor and non-tumor samples immediately freeze in Liquid Nitrogen

Question 5

Procedure for rapid microscopic analysis during operation?

Answer 5

Intra-operative frozen section

Question 6

Indications for Intraoperative frozen sections

Answer 6

• Identify type of tissue
• Confirm malignancy to guide immediate management
• Assess extent of malignancy
• Assess sentinel LN
• Check resection margins
• Confirm sufficient tissue is present for diagnosis on permanent sections

Question 7

Contraindications for Intraoperative frozen sections

Answer 7

• Frozen section diagnosis has no implications for decision making
• High risk of infection by biopsy
• Difficult to get enough tissue
• Confirm an earlier diagnosis
• ‘rare’ disease

Question 8

4 limitations of intraoperative frozen sections

Answer 8

• Cannot do optimal tissue fixation > cannot do proper microscopic assessment
• Limited view of frozen section samples
• Lots of tissue artifacts that interfere with interpretation
• Fatty, edematous, ossified or calcified tissue

Question 9

Fixation technique for intraoperative frozen sections

Answer 9

Not paraffin wax

Sections cut inside cryostat and frozen in liquid nitrogen

Question 10

Examples of intraoperative frozen sections artifacts

Answer 10

Ice crystal artefact (interferes with edematous tissue)

Under freezing (interfere with fatty tissue - too soft to cut)

Over freezing (tissue hardening, holes and folds)

Question 11

Ice crystal artefact on intraoperative frozen sections interferes with Dx of which cancers

Answer 11

Hydropic uterine smooth muscle tumors

Papillary carcinoma of thyroid

Question 12

Next step if intraoperative frozen sections cannot yield Dx?

Answer 12

Convert to paraffin sections for proper assessment

Defer Diagnosis

Question 13

Major cause of false negative resection margins in intraoperative frozen sections

Answer 13

Tumor cells not visible in the frozen section

Lymphoid cells obscure the cancer cells

Question 14

Minimally invasive method for screening test?
3 types?
Fixation?

Answer 14

Cytopathology

1. Exfoliative sample
2. Scrapings
3. Fine Needle Aspirates

Add fixative (50% alcohol) or send fresh to lab

Question 15

Drawbacks to FNAC

Answer 15

• Operator dependent
• Common problem: inadequate sample, thick smears
• Air-drying artefacts

Question 16

2 cancers that can use FNAC to Dx?

2 ways to localize tumor for FNAC?

Answer 16

Breast cancer
Thyroid cancer

Assess location by US (deep-seated) or palpation (superficial)