Neoplasia I: Definition & Classification Flashcards
What is neoplasia?
Abnormal mass of tissue, the growth of which is uncoordinated with that of normal tissues and persists after the stimulus is removed.
What is a tumour?
Swelling, generally without inflammation, caused by an abnormal growth of tissue whether benign or malignant.
What are the major categories for cell types of origin for tumours?
-Epithelium
-Connective tissue
-Lymphoid/haematopoietic tissue
-Germ cells
What is tumour differentiation?
Tumour differentiation refers to how well the tumour resembles its normal counterpart, both morphologically & functionally.
Are well differentiated lesions more or less proliferative than the poorly differentiated ones?
Generally, well-differentiated lesions are less proliferative & less aggressive, with less potential for metastatic spread than their poorly differentiated counterparts.
There are exceptions
What are the different grades of tumours?
Grade 1/well differentiated
Grade 2/moderately differentiated
Grade 3/poorly differentiated
What are some important definitions regarding abnormalities of growth & can you give examples of each one
Hyperplasia: Increase in the number of cells in a tissue.
Eg: Bone marrow cells in people living at high altitudes
Hypertrophy: Increased in the size of cells in a tissue eg: Bodybuilders/athletes
Atrophy: Reduction in the size of cells in a tissue. Eg: Muscle atrophy in a dis-used limb
Involution: Breast tissue on cessation of breastfeeding
Metaplasia: A change from one to another normal differentiated cell type within a tissue. Eg: Barrett’s oesophagus
Dysplasia: A state in some tissues which denotes an increased risk of
malignant change. Eg: Cervical screening
How do you differentiate benign neoplasia from malignant neoplasia?
Benign:
-Well differentiated, likely to resemble tissue of origin
-Slow growth
-Mitotic figures rare and normal
-Well demarcated
-Expansible growth
-Do not metastasise
Malignant:
-Spectrum of differentiation from well to poorly differentiated
-Growth rate variable and less predicable
-Mitotic figures may be numerous and atypical
-Poorly demarcated
-Locally invasive
-Regional and distant metastasis
Metastasise = Spread to other parts of the body
Which tumours are more common?
epithelial
What are the general rules for tumour nomenclature ?
Generally speaking for epithelial tumours, if the suffix is carcinoma it’s malignant and if it’s papilloma or adenoma, it’s benign
For mesenchymal tumours, if the suffix is sarcoma, it’s malignant and if it’s just -oma, then it’s benign
The prefix of the tumour will always refer to the type of tissue of origin e.g. osteoma (osteo meaning bone)
What are some individual tumour names we should be familiar with?
Lymphoma- malignant tumours of the lymphoid system
Melanoma- malignant tumour of melanocytes
Leukaemia- malignant tumour of bone marrow cells
Teratoma- a tumour which includes elements of all 3 embryonic germ layers
Hamartoma- a developmental anomaly (not actually a tumour)
What can cause tumours?
Genetic predisposition, surrounding tissues e.g. inflammation, environmental/social/infectious factors
Some cancers can also be caused by viruses and infection
what cancer is caused by a virus?
Cervical, oropharyngeal and anal squamous cell carcinoma: high risk
HPV
“Oropharyngeal HPV associated squamous cell carcinoma”
Nasopharyngeal carcinoma and Burkitts lymphoma: EBV
Kaposi sarcoma: HHV-8 (human herpes virus 8
what cancers are associated with infections and inflammation?
Hepatitis and liver cancer (hepatocellular carcinoma)
H pylori and gastric cancer (adenocarcinoma)
Pancreatitis and pancreatic cancer (adenocarcinoma)
What are the different ways that malignant tumours spread?
Direct- local infiltration
Lymphatic- to regional lymph nodes
Haematogenous- lungs, liver, bone
Peri-neural- salivary tumours
Trans-coelomic- pleura, pericardium, peritoneal
What forms the lining of the oral mucosa?
Squamous epithelium
How do squamous cells infiltrate & become malignant cells?
They undergo genetic changes & lose those tight attachments to each other
They disrupt/dissolve the basement membrane & then they gain the ability to enter connective tissues and acquire mobility
What are the sequence of events that makes it go from a primary to a metastatic tumour?
Tumour cells secrete vascular growth factors- encourages angiogenesis (formation of new blood vessels)
Well vascularised tumour has good supply of nutrients & oxygen so can keep growing at an abnormal rate
Large sheets of tumour cells detach by downregulating proteins that normally mediate their connections
Then, invasion of connective tissues towards blood vessels & lymphatic channels happens and this involves acquiring mobility
Evasion of host defences follows
Then, migration through vessel wall & a formation of a tumour embolus happens as well as further evasion of host defences
Next we have adhesion to vessel wall, and they can utilise processes very similar to inflammatory cell extravasation to gain access to the tissues
Finally, there is invasion of new host tissue & angiogenesis again
What are some non-malignant effects of tumours?
Increased tendency to thrombosis
Cellular overactivity
Paraneoplastic phenomenon - set signs and symptoms that are a consequence of the presence of the tumour but not directly attributable to it.
What are some factors that affect prognosis of tumours?
-Tumour type
-Site and size; resectability
-Differentiation
-Degree of cellular atypia (cellular state of not being typical)
-Depth and extent of invasion
-Mitotic index and degree of mitotic atypia
-Regional lymph node involvement
-Distant metastasis
What prognostic index is used for colorectal cancer?
Dukes staging:
Dukes A being confined to the bowel wall whereas Dukes D is distant metastases
What prognostic index is used for melanoma?
Clark Levels (level 1 being the least invasive and level 5 being the most)
What prognostic index can we use for histological images?
Mitotic count,
How do you diagnose a tumour?
You need a tissue sample for diagnosis of presence of a tumour and also to sub-type it
Radiology can help to define size, extent and structures involved and might give some clues as to the tumour type Tissue:
-Fine needle aspirate (FNA)
-Histology (biopsy)
What is screening?
The systematic search for cancer in people who have no signs or symptoms of cancer.
What are a couple of issues with screening?
False positives
Over diagnosis e.g some people with papillary thyroid cancer are not affected at all during their lifetime.
Why is screening common for cervical, breast, & colorectal cancer but not for lung, thyroid, & prostate cancer?
Lung: CT screening 70-90% patients had 1 false positive result– remember radiological examination does not diagnose cancer and consider the radiation dose for a CT chest
Prostate: PSA screening 25-30% of patients had 1 false positive result – equally a simple blood test cannot differentiate a hyperplastic prostate from a malignant one
What is the difference between staging and grading?
Grading is tumour differentiation (well, moderate, poor)
Staging uses a T N M classification (T-tumour; N-lymph nodes; M-metastasis) and it’s all about prognosis
