Intro to neoplasia

Question 1

Define neoplasia

Answer 1

Process of abnormal (increased) cell proliferation

Question 2

Define neoplasm

Answer 2

Abnormal mass of tissue due to abnormal cell proliferation
Also known as a tumour

Question 3

What are the 3 types of neoplasm/tumour?

Answer 3

Benign
Pre-malignant
Malignant (cancer)

Question 4

Define oncogenesis

Answer 4

process of gradual steps toward tumour development

Question 5

What is the difference between pre-malignant and malignant tumours?

Answer 5

The basement membrane is still intact and the tumour has not spread to other tissues in pre-malignant

Question 6

How do we determine if a mass is neoplasia?

Answer 6

Take a sample for histology

Question 7

What should we examine when determining if a sample is neoplasia?

Answer 7

Organisation of tissue structure
Degree of cellularity
Nuclear to cytoplasmic ratio
Nuclear morphology
Necrosis
Mitotic index
Individualisation of cells
Invasiveness of cells

Question 8

What is the difference between benign and malignant tumours

Answer 8

Benign tumour = non-invasive
Malignant tumour = invades surrounding tissue

Question 9

What are the characteristics of benign tumours. Give an example.

Answer 9

Slow-growing mass
Good demarcation from surrounding tissue (capsule)
Does not spread (no metastasis)
Minimal necrosis

Question 10

Describe the characteristics of malignant tumours. Give an example

Answer 10

Can grow rapidly
Invasiveness to surrounding tissue
Can spread to other sites in body (metastasis)
Increased necrosis

Question 11

Why does necrosis occur in malignant tumours?

Answer 11

Tumours grow too rapidly for the blood supply to support the centre of the mass => death of cells

Question 12

Why do tumours often get infected?

Answer 12

Loss of blood supply to centre => no WBCs

Question 13

What is the cytological criteria of malignancy?

Answer 13

Question 14

Complete this table comparing the features of benign vs malignant tumour cells

Answer 14

Question 15

Fill in this table comparing the features of benign and malignant tumours

Answer 15

Question 16

Which genes control cell proliferation?

Answer 16

Proto-oncogenes - promote proliferation
Tumour suppressor genes - suppress proliferation or induce cell death

Question 17

How does cell proliferation become dysregulated?

Answer 17

Proto-oncogenes mutate into oncogenes
Oncogenes code for oncoproteins that promote cell division despite absence of promotion signals and presence of normal check point controls to suppress division

Tumour suppressor genes can become mutated so they no longer supress cell division => neoplasia

Question 18

What factors contribute to oncogenesis?

Answer 18

Genetic
Epigenetic
Environmental

Question 19

Why does cancer occur more commonly in older patients?

Answer 19

Multiple hit hypothesis - one mutation not enough to cause neoplasia on its own - takes time for mutations to develop and accumulate

Question 20

What are the hallmarks of cancer cells?

Answer 20

Question 21

What is carcinogenesis?

Answer 21

Some some of mutation in a cell that causes neoplasia

Question 22

What is an intrinsic factor of mutagenesis?

Answer 22

Normal by-products of cell metabolism that cause DNA damage
e.g. reactive oxygen species (ROS) a.k.a free radicals

Question 23

What are some extrinsic factors of mutagenesis?

Answer 23

Question 24

Describe direct-acting chemical agents that act as an extrinsic factor of mutagenesis

Answer 24

Cause mutagenesis in the form in which they enter the body
e.g. nitrosamines in tobacco smoke

Question 25

Describe indirect-acting chemical agents that act as an extrinsic factor of mutagenesis

Answer 25

Need to be activated by enzymes in the body to cause mutagenesis (Most important enzyme is cytochrome P450 in the liver) Also called procarcinogens e.g. ptaquiloside in bracken fern => bladder tumours in cattle

Question 26

Describe physical agents as an extrinsic factor of mutagensesis

Answer 26

Cause direct DNA damage and ROS generation - ROS can cause G to T transversion Key physical agent is radiation

Question 27

Describe radiation as an extrinsic factor of mutagenesis

Answer 27

All types of radiation are complete carcinogens - Initiators of oncogenesis - Also promoters of oncogenesis through continued exposure

Question 28

Describe ultraviolet radiation (sunlight) as an extrinsic factor of mutagenesis

Answer 28

Ultraviolet radiation (sunlight) causes: - Pyrimidine dimer formation (results in misreading during transcription) - ROS generation

Question 29

Describe the direct mechanisms of oncogenic viruses

Answer 29

Dominant oncogene mechanism - Mutation in viral gene causes host cells to produce oncoprotein e.g. Feline leukaemia virus Insertional mechanism - No oncogene in virus - Insertion of viral DNA into host cells activates proto-oncogenes => oncogenes e.g. Avian leukosis virus

Question 30

Describe indirect mechanisms of oncogenic mechanisms

Answer 30

Suppress host immune system e.g. Gallid herpesvirus-2 (Marek’s disease) Directly stimulate host cell proliferation e.g. Leporipoxvirus (Squirrel fibroma virus)`

Question 31

Define metastasis

Answer 31

movement of cancer cells from one tissue or organ to another

Question 32

Describe the process of metastasis

Answer 32

Cancer cells break away from primary tumour Cells travel through blood and lymphatic vessels (usually) to new tissues/organs distant from primary tumour Secondary tumours (metastases) develop in new organs

Question 33

Define metastases

Answer 33

new cancerous growths at distant sites

Question 34

Give an example of a highly metastatic and poorly metastatic tumour

Answer 34

Some tumours highly metastatic e.g. melanoma Some are poorly metastatic e.g. squamous cell carcinoma

Question 35

Why is it important to identify a tumour when it is small?

Answer 35

Generally- the bigger the tumour, the more likely it is to metastasise

Question 36

What are the 3 pathways of metastasis?

Answer 36

haematogenous lymphatic transcoelomic

Question 37

Describe the haematogenous pathway of metastasis

Answer 37

Cancer cells travel in blood vessels Usually thinner-walled veins rather than arteries Most common route for sarcomas Ultimately enter lungs and liver

Question 38

Describe the lymphatic pathway of metastasis

Answer 38

Cancer cells travel in lymphatic vessels Lymph node(s) closest to the tumour are colonised first These first lymph nodes develop the largest tumours Most common route for carcinomas

Question 39

Describe the transcoelomic pathway of metastasis

Answer 39

Cancer cells spread across the surface of abdominal and thoracic structures Route used by mesotheliomas and ovarian adenocarcinomas

Question 40

What are the fundamental steps of metastasis?

Answer 40

Intravasation - into vessels Extravasation - out of vessels at new site Colonisation - expansion into macroscopic masses