Neoplasia 1

Question 0

Describe and compare benign and malignant tumours (macroscopic and microscopic features)

Answer 0

Macroscopic:
Benign - grow in a confined local area, have a pushing outer margin
Malignant - irregular outer margin and shape, may show areas of necrosis and ulceration
Microscopic:
Benign - cells that closely resemble the parent tissue, well differentiated
Malignant - range from well to poorly differentiated,
Cells with no resemblance to any tissue are anaplastic
With worsening differentiation, individual cells have increasing nuclear size and nuclear to cytoplasmic ratio, nuclear hyperchromasia, more mitotic figures and pleomorphism.
Mild, moderate and severe dysplasia indicates worsening differentiation

Question 1

Define the terms ‘neoplasia’, ‘dysplasia’, ‘tumour’, ‘cancer’ and ‘metastasis’

Answer 1

Neoplasia - an abnormal growth of cells that persists after the initial stimulus is removed, change is irreversible
Malignant neoplasia - an abnormal growth of cells that persists after the initial stimulus is removed and invades surrounding tissue with potential to spread to distant sites
Dysplasia - pre-neoplastic alteration in which cells show disordered tissue organisation, change is reversible
Tumour - any clinically detectable lump or swelling
Cancer - malignant neoplasm
Metastasis - malignant neoplasm that has spread from its original site to a new non-contiguous site

Question 2

Describe the alterations to DNA which cause neoplasia

Answer 2

Accumulated mutations in somatic cells.
The mutations are caused by initiators, which are mutagenic agents, and promoters, which cause cell proliferation.
Initiators and promotors result in an expanded, monoclonal population. A neoplasms emerges by progression (accumulation of more mutations)
Chemicals, infections and radiation are the main initiators but some can act as promotors.
Some neoplasm mutations can be inherited.
Alterations occur in proto-oncogenes (–> oncogenes) or tumour suppressor genes (–> permanently inactivated)

Question 3

Describe clonality of neoplasms

Answer 3

Neoplasms are monoclonal - they all originated from single founding cell.
Evidence came from the study of G6PD in women.

Question 4

Distinguish between in-situ and invasive malignancy

Answer 4

In-situ - no invasion of epithelial basement membrane

Invasive - penetrated through basement membrane

Question 5

Explain the naming of neoplasms

Answer 5

Benign neoplasm ends in ‘-oma’
Malignant neoplasms ends in ‘-carcinoma’ (if it’s epithelial malignant) or ‘-sarcoma’ (if it’s stromatolites malignant)
Leukaemia - malignant neoplasm of blood forming cells arising in bone marrow
Lymphoma - malignant neoplasms of lymphocytes, mainly affecting lymph nodes
Germ line neoplasms arise from pluripotent cells, mainly testes or ovaries
Neuroendocrine tumours arise from cells distributed in the whole body
‘-blastomas’ occur mainly in children and are formed from immature precursor cells

Question 6

Describe the basic histological types of benign and malignant neoplasms (adenoma, papilloma, carcinoma adeno, squamous, transitional, benign mesenchymal tumours, sarcomas, gliomas, lymphomas, germ line tumours, tumours of white cells)

Answer 6

Epithelial neoplasms (benign):
Stratified squamous - squamous papilloma, tumour with finger-like projections e.g. skin, buccal mucosa
Transitional - transitional cell papilloma e.g. bladder mucosa
Glandular - adenoma e.g. adenomatous polyp of the colon
Epithelial neoplasms (malignant):
Squamous cell carcinoma e.g. skin, larynx, oesophagus
Transitional cell carcinoma e.g. bladder, ureter
Adenocarcinoma e.g. Stomach, colon, lung, prostate breast, pancreas
Basal cell carcinoma e.g. skin
Connective tissue neoplasms (benign):
Leiomyoma (smooth muscle), fibroma (fibrous tissue), osteoma (bone), chondroma (cartilage), lipoma (fat), neuroma (nerve), neurofibroma (nerve sheath), glioma (glial cells)
Connective tissue neoplasms (malignant):
Leiomyosarcoma (smooth muscle), fibrosarcoma (fibrous tissue), osteosarcoma (bone), chondrosarcoma (cartilage), liposarcoma (fat), malignant glioma (glial cells)
Lymphoid neoplasm - lymphoma (Hodgekins disease and Non Hodgekins lymphoma)
Haemotopoeitic - acute and chronic leukaemia
Testis - malignant teratoma, seminoma
Ovary - benign teratoma (dermoid cyst)

Question 7

List the key differences between neoplastic cells and normal cells

Answer 7

Self sufficient growth signals (gene amplification)
Resistance to anti-growth signals (gene deletion)
Grow indefinitely (telemorase gene activation)
Induce new blood vessels (VEGF expression activation)
Resistance to apoptosis (gene translocation)
Invade and produce metastases E-cadherin expression altered)