Characteristics of tumours

Question 1

What is histiogenesis?

Answer 1

The differentiation of cells into specialised tissues and organs during growth from undifferentiated cells (the 3 primary germ layers)

Question 2

What is histiogenesis relating to tumours?

Answer 2

Histogenic classification – classification of the tumour by the specific cell or tissue of origin

• Epithelial cells – carcinomas
• Connective tissues – sarcomas
• Lymphoid/haematopoietic organs – lymphomas/leukaemias

Question 3

What is differentiation?

Answer 3

The extent that neoplastic cells resemble the corresponding normal parenchymal cells, morphologically and functionally

Question 4

What are the characteristics of differentiation of benign tunours?

Answer 4

• usually well-differentiated

- Mitoses are rare

Question 5

What are the differentiation characteristics of malignant tumours?

Answer 5

• Wide-range of parenchymal differentiation

- Most exhibit morphologic alterations showing malignant nature

Question 6

What is anaplasia?

Answer 6

Neoplasms comprised of poorly-differentiated cells are described as anaplastic
“Telltale sign of malignancy”

Question 7

What are the morphological changes that might occur during neoplasia?

Answer 7

• Pleomorphism
• Abnormal nuclear morphology
• Mitoses
• Loss of polarity
• Other changes

Question 8

What is pleomorphism?

Answer 8

Variation - Size, shape
Huge differences
- Small cells with little differentiation
- Large cells with one massive nucleus
- Large cells with multinucleation

Question 9

What abnormal nuclear morphology might be seen in cancer?

Answer 9

Nuclei appear too large for the cell that they are in
Nuclear to cytoplasmic ratio 
-Can reach 1:1 rather than usual (1:4 or 1:6)
Variability in nuclear shape
-Irregular
-Making pictures (raisins, faces etc.)
Chromatin distribution
-Coarsely clumped
-Along cell membrane
Hyperchromatism
-Dark colour
Abnormally large nucleoli

Question 10

What are mitoses?

Answer 10

Atypical, bizarre mitotic figures seen in malignancy

• Tripolar
• Quadripolar
• Multipolar spindles

Question 11

What are the features of loss of polarity?

Answer 11

• Orientation of cells disturbed

- Disorganised growth

Question 12

What is the grade of a tumour related to?

Answer 12

Closely related to differentiation / clinical behaviour

Well differentiated = low grade / grade 1
Moderately differentiated = intermediate / grade 2
Poorly differentiated = high grade / grade 3

Question 13

What is the stage of a tumour related to?

Answer 13

How far the cancer has spread throughout the body.

Question 14

How is the level of differentiation within a tumour related to a possible change in function?

Answer 14

The better the differentiation of the tumour the better the retention of function i.e. a large, benign endocrine tumour may secrete large amounts of hormone.

Question 15

What kinds of local invasion are associated with malignancies?

Answer 15

• Infiltration
• Invasion
• Destruction

Question 16

What kinds of local invasion are associated with benign neoplasia?

Answer 16

• Cohesive expansile masses
• Localised to site of origin
• No capacity to infiltrate, invade or metastasise

Question 17

What histological features might represent local invasion of a benign tumour?

Answer 17

• Rim of compressed fibrous tissue
• ECM deposited by stromal cells activated by hypoxia from pressure of tumour
• Tissue plane
  
  • Discrete, moveable
  • Easily palpable
  • Easily excised

Question 18

What are metastases?

Answer 18

Spread of a tumour to sites physically discontinuous with the primary tumour.

Question 19

What are the pathways by which metastases can occur?

Answer 19

• Direct seeding
• Lymphatic spread
• Haematogenous spread

Question 20

What is direct seeding?

Answer 20

Neoplasm penetrates a natural open field without physical barriers
Eg peritoneal cavity, pleural, pericardial, subarachnoid, joint spaces

Can remain confined to surface of peritoneal structures without penetrating
Eg pseudomyxoma peritonei

Question 21

What is lymphatic spread?

Answer 21

Lymphatic Spread
Most common pathway
Tumours do not contain lymphatic channels
Lymphatic vessels at the tumour margins

Question 22

What are sentinal nodes?

Answer 22

The first node in a regional lymphatic basin that receives lymph flow from the primary tumour
Identified by: injection of radiolabelled tracers/coloured dyes

Question 23

Why might an enlarged node in a cancer patient not have cancer in it?

Answer 23

Drainage of tumour cell debris and tumour antigens induces reactive change in nodes

Question 24

What are the features of haematogenous spread?

Answer 24

• Typical of sarcomas
• Also seen in carcinomas
• Veins more easily penetrated
• Blood-borne cells follow the venous flow draining site of the neoplasm
• Often come to rest in first encountered capillary bed
• Liver (portal) and lungs (caval) most frequently involved

Question 25

What is the desmoplastic reaction?

Answer 25

Fibrous stroma formation due to induction of connective tissue fibroblast proliferation by growth factors from the tumour cells

Stroma contains:
Cancer-associated fibroblasts 
Myofibroblasts 
Blood vessels
Lymphocytic infiltrate

Question 26

Why might a malignant tumour cause cachexia?

Answer 26

Tumour-derived humoral effects that interfere with protein metabolism.

Question 27

What is the Warburg effect?

Answer 27

Cancer cells produce energy by high rate of glycolysis with fermentation of lactic acid
Used in imaging – PET scanning (FDG uptake)