2.15 - Cancer

Question 1

What is a tumour?

Answer 1

• any kind of mass forming lesion
• may be neoplastic or non-neoplastic (hamartomas, inflammatory e.g. nasal polyps and heterotopias)

Question 2

What is a neoplasm?

Answer 2

• the autonomous growth of tissue which have escaped normal constraints on cell proliferation
• autonomous means they don’t require external stimuli and grow on their own

Question 3

What are the two types of neoplasms?

Answer 3

• benign (remain localised) or malignant (invade locally and/or spread to distant sites - metastasis)
• cancers are malignant neoplasms

Question 4

What do benign neoplasms look like?

Answer 4

• well differentiated and look like normal tissue - neoplasm is sharply demarcated from surrounding tissue
• cannot tell the difference between benign neoplasm and surrounding tissue
• fibroadenomas in young women are benign neoplasms that are mobile (can move them around as they aren’t stuck to the skin or the underlying pectoralis muscles)

Question 5

What do malignant neoplasms look like?

Answer 5

• irregular margins
• fixed to muscle/skin which shows that it is invasive as it is invading locally
• e.g. malignant neoplasm in breast, grows into the fat

Question 6

What is important to note about deaths caused by malignant vs benign tumours?

Answer 6

• many malignant tumours rarely cause death (especially skin cancers - invade locally but low chance of metastasising) and some benign tumours do kill (due to their location e.g. brain)
• malignant skin cancer is very common and invades locally but has low chance of metastasising so can be controlled easily

Question 7

What are hamartomas?

Answer 7

• localised benign overgrowths of one or more mature cell types e.g. in the lung
• they represent architectural but not cytological abnormalities
• e.g. lung hamartomas are composed of cartilage and bronchial tissue - there is nothing special about the tissue itself but in the way they are arranged –> would cause a lump on an X-ray

Question 8

What are heterotopias?

Answer 8

• normal tissue being found in parts of the body where they are not normally present
• e.g. bits of pancreas in the wall of the large intestine (whereas it should be in the retroperitoneum)
• if we look endoscopically into stomach we can see a lump but if we look under a microscope we can tell it is just a heterotopic pancreas

Question 9

What is the primary and secondary descriptions of neoplasms based on?

Answer 9

• primary - the cell origin
• secondary - whether it is benign or malignant
  E.g. tumours of the cartilage are described as:
• chondromas (benign) or chondrosarcomas (malignant)
• chondro means cartilage
• oma means benign and sarcoma means malignant (soft tissue) tumour

Question 10

Epithelial neoplasms

Answer 10

• type of epithelium - benign tumour - malignant tumour - examples
• squamous - squamous papilloma - squamous cell carcinoma - skin, oesophagus, cervix
• glandular - adenoma - adenocarcinoma - breast, colon, pancreas, thyroid
• transition (can deal with changes in volume) - transitional papilloma - transitional cell carcinoma - bladder

Question 11

Connective tissue neoplasms

Answer 11

• type of connective tissue - benign tumour - malignant tumour - examples
• smooth muscle - leiomyoma - leiomyosarcoma - uterus, colon
• bone - osteoma - osteosarcoma (osteogenic sarcoma) - arm, leg

Question 12

Haematological neoplasms

Answer 12

• haematological neoplasms - benign tumour - malignant tumour - examples
• lymphocytes - extremely uncommon - lymphoma (based in lymph nodes) - gastric lymphoma
• bone marrow - extremely uncommon - leukaemia - acute lymphoblastic leukaemia, chronic myeloid leukaemia

Question 13

What are teratomas?

Answer 13

• tumours derived from germ cells and can contain tissue derived from all three germ layers (ectoderm, mesoderm, endoderm)
• they may contain mature/immature tissues and even cancers
• will be in male/female reproductive tract because of germ cell involvement
• benign teratomas contain hair and are lined by skin - these are normal adult tissues, just in the ovary where they shouldn’t be = mature teratoma

Question 14

What malignant tumours are there that end in ‘oma’?

Answer 14

• (malignant) lymphoma
• (malignant) melanoma
• hepatoma (liver cell cancer)
• teratoma (can contain mature/immature elements or carcinoma, not all are malignant)

Question 15

What are the differences between benign and malignant tumours?

Answer 15

• invasion
• metastasis
• differentiation
• growth pattern

Question 16

What is invasion?

Answer 16

• direct extension into the adjacent connective tissue and/or other structures e.g. blood vessels
• this is what distinguishes dysplasia/carcinoma in situ from cancer - dysplasia is non-invasive
• carcinoma in situ is the most severe degree of dysplasia but still in situ (in its place) so not invaded other tissues, so not cancer
• e.g. invasive squamous cancer - non-invasive part is dysplastic squamous epithelium, invasive part has evoked a lymphoid response and is cancerous

Question 17

What is metastasis?

Answer 17

• spread via blood vessels etc to other parts of the body
• all malignant tumours have the capacity to metastasise although they may be diagnosed before they have done so
• metastasis makes it harder to treat cancer than if it stays in one local area - need chemotherapy and prognosis is worse

Question 18

What is differentiation?

Answer 18

• how much the cells of the tumour resemble the cells of the tissue it is derived from
• tumour cells tend to have larger nuclei (and hence higher nuclear-cytoplasmic ratio) and more mitoses than normal tissue they’re derived from
• they may have abnormal mitoses (e.g. tripolar) and marked nuclear pleomorphism (variability in nuclear size and shape)

Question 19

What are the differences between cancerous looking cells and normal cells?

Answer 19

• large, variably shaped nuclei
• many dividing cells
• disorganised arrangement
• variation in size and shape
• loss of normal features

Question 20

What is the growth pattern?

Answer 20

• how much does the architecture of the tumour resemble the architecture of the tissue it is derived from
• tumours have less well-defined architecture than the tissue they are derived from
• the less well-differentiated a tumour is, the worse the architecture will get

Question 21

What is the progression of a cancer like? e.g. colonic tumour

Answer 21

• starts off as adenoma - benign tumour of glandular epithelium - hyperproliferation –> adenomatous polyps
• then severe dysplasia occurs (not cancer yet as it is still confined to mucosa) - pre cancerous polyp
• then it becomes an adenocarcinoma as the tumour invades the underlying tissue
• then finally the tumour grows more all the way through the wall = invasive cancer

Question 22

By which routes do tumours spread?

Answer 22

• direct extension
• haematogenous
• lymphatic
• transcoelomic
• perineural

Question 23

What is direct extension?

Answer 23

• associated with a stromal (connective tissue) response to the tumour
• includes fibroblastic proliferation (a demoplastic response), vascular proliferation (angiogenesis) and an immune response

Question 24

What is the haematogenous route?

Answer 24

• via blood vessels - usually venules and capillaries due to thinner walls
• most sarcomas metastasise first via blood vessels
• vascular invasion: e.g. if left blood vessel has RBCs but right one doesn’t, and has tumour instead

Question 25

What is the lymphatic route?

Answer 25

• via lymphatics to lymph nodes and beyond
• the pattern of spread is dictated by the normal lymphatic drainage of the organ in question
• most epithelial cancers metastasise first via the lymphatics
• e.g. carcinomas in lateral aspect of breast will go to lymph nodes in axilla because that is the lymphatic drainage point

Question 26

What is the transcoelomic route?

Answer 26

• via seeding of body cavities
• commonest examples are the pleural cavities (for intrathoracic cancers e.g. lung) and peritoneal cavities (for intra-abdominal cancers e.g. GI tract, stomach)
• peritoneal cavity is low resistance zone, moist and constantly moving = facilitates tumour spread

Question 27

What is the perineural route?

Answer 27

• via nerves
• underappreciated route of cancer spread
• good way for tumours to spread as low resistance pathway and for some cancers like liver ones, it is common to spread this way

Question 28

How do we assess tumour spread?

Answer 28

• clinically - examining patient e.g. examining lymph nodes of patient / lump on breast
• radiologically - CT scans, planning X-ray
• pathologically - definitive means of staging tumours (how far they have spread)

Question 28

How do we describe tumour spread (stage)?

Answer 28

• T = tumour - tumour size or extent of local invasion
• N = nodes - number of lymph nodes involved
• M = metastases - presence of distant metastases
• this is the TNM system and the details are different for each type of tumour
• dictate patient prognosis and treatment

Question 29

What is the meaning of grade and stage?

Answer 29

• grade - how differentiated is the tumour?
• stage - how far has the tumour spread?
• the worse the grade/stage, the worse the prognosis
• in terms of tumour prognosis, stage is more important than grade
• if tumours are high grade, they tend to be high stage - main prognostic factor