Neoplasia including classification of tumours Flashcards
(36 cards)
What is a neoplasm?
An abnormal mass of tissue, growth of which is excessive and is unco-ordinated with that of normal tissues. It persists after the provoking stimulus is removed
Define invasion
Uncontrolled growth into CT - defining feature of malignant tumours
Define metastasis
Spread distant from primary tumour
Define differentiation
The extent of resemblance of normal cells/ tissue is very variable
Define cytology
Features of individual cells - often very abnormal
Classification of neoplasms
By clinical behaviour -benign -malignant By histogenesis (tissue of origin) -epithelial - lining or glandular -mesenchymal - various types
Growth pattern of benign or malignant tumours
Benign: expansion, encapsulated, localised
Malignant: invasion, no capsule, metastasis
Growth rate of benign and malignant tumours
Benign: slow
Malignant: more rapid, but variable
Histology of benign and malignant tumours
Benign: resembles tissue of origin, uniform cell/ nuclear shape and size, few mitoses
Malignant: variable resemblance to tissue of origin, cellular and nuclear polymorphism, many mitoses, abnormal
Clinical effects of benign and malignant tumours
Benign: localised, local pressure, excision cures
Malignant: infiltration and spread, local pressure, excision may not cure
Components of benign tumour
Tumour cells Stroma (supporting CT) including fibroblasts and BVs Capsule -most, but not all tumours -may be incomplete
Effects of benign tumours
Pressure Obstruction Function - especially hormone secretion -these vary by site and tumour -effect is not always 'benign'
Pathology of malignant tumours
Tumour cells -invade, underlying tissues -cytologically abnormal -differentiation varies (well, moderate, poor; anaplasia) Stroma -angiogenesis -immune response
Cytology of malignant cells
> no. of irregularly shaped dividing cells > variable shaped nuclei < cytoplasmic vol. relative to nuclei Variation in cell size and shape Loss of normal specialised cell features Disorganised arrangement of cells Poorly defined tumour boundary
Classification of epithelial neoplasms
90% of neoplasms BENIGN Lining: papilloma Glandular: adenoma MALIGNANT Lining: Carcinoma Glandular: Adenocarcinoma
Classification of mesenchymal neoplasms
BENIGN Depends on tissue -e.g. fibroma, osteoma, lipoma, myoma, chondroma -skeletal muscle: rabdomyoma MALIGNANT Sarcoma, depends on tissue -osteo, -leiyomyo
Classification of neoplasms: oddities
Melanoma (melanocytes - malignant)
Lymphoma (arise from WBC)
Leukaemia (arise from bone marrow precursor cells)
Terratoma (germ cell tumours)
-most in testes, most malignant (ovarian tend to be benign)
-can mimic any tissue incl. teeth!
Why do benign tumours arise?
Little known, may be due to inherited factors
Carcinogenesis is multi-step process
Inherited factors: genetic susceptibility to cancer
Inherited cancer syndromes -single mutant genes, often tumour suppressor genes -retinoblastoma, some colon cancers -likelihood of developing cancer extremely high Familial -family clusters of cancers (e.g. BRCA1) -e.g. breast and ovarian cancer -pattern of inheritance unclear -lots of other contributing factors -not only one single gene gives risk Defective DNA repair -> sensitivity to carcinogens -DNA damage isn't repaired -e.g. skin cancer at very young age
Why do malignant tumours arise?
Inherited factors Environmental factors -chemical agents -physical agents -viruses
Two stages of chemical carcinogenesis
- initaition: permanent DNA damage
- promotion: may be reversible, promotes proliferation
Important concepts of chemical carcinogenesis
Pro-carcinogen often metabolised to ultimate carcinogen
Co-carcinogens
Latent period of chemical carcinogenesis
Time from promotion to clinical tumour
Direct chemical carcignogens
Tumour arises at site of carcinogen application
-e.g. smoking and lung cancer
