5.1 cytology

BASICS OF CYTOLOGY

What is cytology ?

Cytology is the study of free cells to diagnose disease.

What are the advantages of cytology ?

• Quick diagnosis

• Same day diagnosis possible for benign lesions

• Cheap compared to histology

• Less invasive for patientS

• Faster recover time

What are the disadvantages of cytology ?

• require high expertise for interpretation

• May be sensitive and specific than histology

• Ancillary tests are sometimes not possible

Why are the advantages of histology compared to cytology ?

• Gold standard for diagnosis

• Easier to perform ancillary tests

• Allows grading of tumours

• Determines receptor status of malignant lesions

• Allows special stains, immunocytochemistry and molecular panels

What are the disadvantages of histology?

• Same day results are difficult

• More expensive

• More invasive for patients

Cytology Sample Collection

How can cytology diagnostic samples be obtained?

• Scraping a tissue surface

• Cells from urine or sputum

• Brushing or washing cells during surgical procedures

• Aspiration with a needle from lumps or lesions

What sites can cytology samples be taken from?

• Bladder

• Pancreas

• Bile duct

• Pleural fluid

• Pericardial fluid

• Peritoneal fluid

• Synovial fluid

• Breast

• Thyroid

• Salivary and parotid glands

• Hydrocoele fluid

• Lymph nodes

Processing Cytology Samples

What happens when fluid samples are centrifuged?

Centrifugation separates components:

1. Plasma → rises to the top

2. Buffy coat → middle layer containing white blood cells and tumour cells

3. Red blood cells → bottom layer (small and dense)

Cells from the buffy coat are pipetted and spread on a glass slide as a monolayer for staining.

What fluids are commonly analysed in cytology?

• Urine

• CSF

• Serous effusions
  

  • Lung

  • Abdomen

  • Cysts

What is a cytocentrifuge (cytospin)?

A technique used when fluids contain very few cells, concentrating them onto a slide for microscopy.

Cytology Stains

What is the Romanowsky stain used for?

• Used on air-dried specimens

• Provides good cytoplasmic detail

• Consists of:
  

  • May-Grünwald

  • Giemsa

What is the Papanicolaou stain used for?

• Used on wet-fixed specimens

• Provides good nuclear detail

• Consists of:
  

  • Haematoxylin

  • EA50

  • OG6

Cerebrospinal Fluid Cytology

What is cerebrospinal fluid (CSF)?

A clear watery fluid surrounding the brain and spinal cord.

Where is CSF located?

• Subarachnoid space

• Central canal of the spinal cord

What is the origin of CSF?

It is an ultrafiltrate of blood plasma.

Why is cancer spread to the CNS serious?

It causes:

• Neurological symptoms

• Rapid mortality

Urine Cytology

What conditions can urine cytology detect?

• Infection

• Inflammatory disease of the urinary tract

• Cancer

• Precancerous conditions

Why is urine cytology commonly performed in haematuria clinics?

Patients with blood in urine (haematuria) are investigated because 10–25% may have cancer, usually bladder cancer.

What additional tests are usually performed alongside urine cytology?

• Ultrasound

• Cystoscopy

Which occupations increase bladder cancer risk?

Workers in the dye industry, especially exposure to aniline dye intermediates such as benzidine.

What is the average latency period for occupational bladder cancer exposure?

23.3 years from exposure to diagnosis.

What lifestyle factor increases bladder cancer risk?

Smoking, due to exposure of bladder cells to chemicals in cigarette smoke.

Types of Bladder Cancer

What is the most common bladder cancer type?

Urothelial (transitional cell) carcinoma – about 90% of cases in the UK.

What are urothelial cells?

Cells lining the bladder that:

• Bunch together when bladder empty

• Stretch into a single layer when bladder fills

What percentage of bladder cancers are squamous cell carcinoma?

About 5%.

What infection increases risk of squamous bladder cancer?

Bilharzia (schistosomiasis) caused by a freshwater parasitic worm.

Where is squamous bladder cancer more common geographically?

• Africa

• Asia

How common is bladder adenocarcinoma?

Very rare – 1–2% of cases.

What cancers can originate in bladder muscle or structural tissue?

Sarcomas

What is small cell carcinoma of the bladder?

An aggressive poorly differentiated neuroendocrine tumour.

Bronchoscopy & Lung Cytology

What is a bronchoscope/endoscope?

A tube with fibreoptics or a camera used to examine airways and obtain samples.

What features does a bronchoscope include?

• Viewing lens

• Instrumentation channel

• Can deliver:
  

  • Water

  • Anaesthetic

  • Biopsy tools

What cytology sampling methods are used during bronchoscopy?

• Bronchial biopsy

• Brush cytology

• Saline washings

What is bronchoalveolar lavage (BAL)?

A procedure where sterile saline washes distal airways and alveoli to collect cells.

When is BAL used?

• Deep lung tumours

• Opportunistic infections (e.g., Pneumocystis carinii in HIV)

• Haemoptysis

• Persistent cough or wheeze

Lung Cancer Types

What are normal bronchial cytology cells?

• Ciliated cells

• Macrophages

• Neutrophils

• Mucus

• RBCs

What is squamous cell lung carcinoma?

• Second most common lung cancer

• Originates in central bronchi

• Often linked to smoking

• Tumours often show central necrosis

• Develops via squamous metaplasia

What is lung adenocarcinoma?

• Most common lung cancer

• Originates from alveolar epithelium

• Often has many DNA mutations

• Often advanced at diagnosis

What is small cell (oat cell) lung carcinoma?

• Highly malignant

• Early metastasis

• Responds well to chemotherapy and radiotherapy

• Neuroendocrine tumour producing ectopic hormones

Thyroid Cytology

What is the thyroid gland?

A butterfly-shaped gland at the base of the neck.

What hormones does the thyroid produce?

• Thyroxine (T4)

• Triiodothyronine (T3)

What functions do thyroid hormones regulate?

• Heart rate

• Blood pressure

• Body temperature

• Energy metabolism

What are thyroid nodules?

Lumps arising within a normal thyroid gland.

How common are thyroid nodules?

About 1 in 10 people develop one by age 50.

What percentage of suspicious thyroid nodules are malignant?

Less than 10%

What technique is used to sample thyroid nodules?

Fine Needle Aspiration (FNA).

Thyroid Pathology

What are follicular cells?

Main thyroid cells that produce T3 and T4 and form cuboidal epithelium around follicles.

What is thyroid colloid?

• Material within thyroid follicles

• Appears blue/mauve with MGG stain

• Seen as background wash

What can excess colloid indicate?

Benign goitre.

What causes most goitres?

Iodine deficiency (≈90%), causing thyroid hyperplasia.

What is Hashimoto’s thyroiditis?

An autoimmune disease causing progressive destruction of the thyroid gland.

Thyroid Cancer

What is the most common thyroid cancer?

Papillary thyroid carcinoma (~85%).

Key features of papillary thyroid carcinoma?

• More common in women

• Age 20–55

• Slow growing

• Forms papillae

• Has nuclear grooves

• Treated mainly with surgery

What is medullary thyroid carcinoma?

Cancer arising from parafollicular (C) cells.

Key features of medullary thyroid carcinoma?

• 25% hereditary

• Causes diarrhoea

• Amyloid stroma

• Parafollicular cell hyperplasia

• Psammoma bodies

Treatment for medullary thyroid carcinoma?

Total thyroidectomy with bilateral neck dissection.

Breast Cytology

How common is breast cancer?

It accounts for 25% of cancers in women.

What is the peak incidence of breast cancer?

Age 55–69

When does breast screening begin?

age 50.

What is the 5-year survival rate for breast cancer

80–90%

What structures make up the breast?

• Fat

• Stroma

• Glandular tissue

• Ductal system

• 6–10 main ducts opening at nipple

Signs of breast cancer?

• Breast lump

• Change in breast shape

• Skin dimpling

• Nipple discharge

• Inverted nipple

• Red or scaly skin patch

What percentage of breast cancers are genetic?

About 5–10%.

Which gene mutation is linked to hereditary breast cancer?

BRCA mutation

What is the most common breast cancer type?

Ductal carcinoma (~80%)

What is DCIS?

Ductal carcinoma in situ – non-invasive cancer confined to ducts

Cytological features of ductal carcinoma?

• Cellular smear

• Less cohesive cells

• No myoepithelial cells

• Crowded epithelial sheets

• Necrosis may be present

What is lobular carcinoma?

Cancer arising from breast lobules, accounting for 10–15% of cases.

Why is lobular carcinoma hard to detect?

• Often does not form a lump

• Low cellularity

• Minimal atypia

• Cells arranged in linear cords

What is fibroadenoma?

common benign breast lesion in young women.

Cytology of fibroadenoma?

• Cellular aspirates

• Large branching sheets of ductal cells

• Myoepithelial cells (“sesame seeds”)

What does HER2 indicate in breast cancer?

A receptor controlling cell growth, division and repair.

What happens in HER2-positive cancers?

• Tumour grows faster

• Spreads more quickly

• But responds well to targeted drugs