Disorder of growth, differentiation and tumour 2024 - Copy.PDF

Disorder of growth, differentiation and tumour ⚫ Growth and differentiation ⚫ Anaplasia ⚫ Neoplasia and tumour Learning outcomes ⚫ To define the terms of growth and differentiation ⚫ Describe the concept of anaplasia ⚫ To understand characteristics and pathogenesis of neoplasia and tumour Diso...

Disorder of growth, differentiation and tumour ⚫ Growth and differentiation ⚫ Anaplasia ⚫ Neoplasia and tumour Learning outcomes ⚫ To define the terms of growth and differentiation ⚫ Describe the concept of anaplasia ⚫ To understand characteristics and pathogenesis of neoplasia and tumour Disorder of growth, differentiation and tumour ⚫ Growth and differentiation ⚫ Anaplasia ⚫ Neoplasia and tumour Growth and differentiation Growth Growth is the process of increase in size resulting from the synthesis of specific tissue components Differentiation A process whereby a cell develops an overt specialised function or morphology which distinguishes it from its parent cells. Tumour differentiation refers to the extent to which neoplastic cells resemble comparable normal cells, both morphologically and functionally Disorder of growth, differentiation and tumour ⚫ Growth and differentiation ⚫ Anaplasia ⚫ Neoplasia and tumour Anaplasia Lack of differentiation is called anaplasia: a hallmark of malignant transformation Means "to form backward" implying a reversion from a high level of differentiation to a lower level Morphological changes of anaplasia Pleomorphism: Variation in size and shape Abundance of DNA; Nuclei are disproportionately large for the cell Mitoses: Mitosis does not necessarily indicate that a tumour is malignant or that the tissue is neoplastic Loss of polarity: The orientation of cells is markedly disturbed Other changes: Formation of tumour giant cells Disorder of growth, differentiation and tumour ⚫ Growth and differentiation ⚫ Anaplasia ⚫ Neoplasia and tumour Neoplasia ⚫ Means the process of "new growth” and a new growth is called a neoplasm ⚫ An abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after cessation of the stimuli which evoked the change ⚫ A tumour (neoplasm): Benign or Malignant ⚫ Cancer is the common term for all malignant tumours Neoplasia Classification of tumours Behavioural classification: benign or malignant Histogenetic classification: cell of origin Nomenclature of tumours ⚫ ⚫ ⚫ ⚫ ⚫ All have the suffix '-oma' Benign epithelial tumours are either papillomas or adenomas Benign connective tissue tumours have a prefix denoting the cell of origin Malignant epithelial tumours are carcinomas Malignant connective tissue tumours are sarcomas Benign tumours Non-invasive and remain localised Slow growth rate Close histological resemblance to parent tissue A fibrous capsule to separate tumour from the host tissue, readily palpable and early movable surgically Malignant tumours Invasive and capable of spreading directly or by metastasis Relatively rapid growth rate Variable histological resemblance to the parent tissue Characteristics of tumours Type Benign Malignant Growth rate Slow Relatively rapid Mitotic activity Low High Histological feature (to original tissue) Good often poor Invasion No Yes Metastases Never Frequent Border circumscribed or encapsulated poorly defined or irregular Necrosis Rare Common Metaplasia ⚫ A reversible change in which one adult cell type (epithelial or mesenchymal) is replaced by another adult cell type ⚫ May represent an adaptive substitution of cells that are sensitive to stress by cell types better able to withstand the adverse environment ⚫ Often in association with tissue damage, repair, and regeneration ⚫ The influences that predispose to metaplasia, if persistent, may initiate malignant transformation in metaplastic epithelium Dysplasia ⚫ A term that literally means disordered growth ⚫ Is encountered principally in metaplastic epithelia ⚫ Dysplastic lesions are often pre-neoplastic ⚫ The architecture of the tissue may be disordered ⚫ Dysplasia does not necessarily progress to cancer Dysplasia Characteristics of dysplasia: Loss in the uniformity of the individual cells and in their architectural orientation Exhibit considerable pleomorphism and often contain hyperchromatic nuclei that are abnormally large for the size of the cell Mitotic figures: abundant and appear in abnormal locations within the epithelium (not confined to the basal layers) Human bronchial biopsies Normal Mild dysplasia Moderate dysplasia Severe dysplasia Metastasis Metastases are tumour implants discontinuous with the primary tumour (only for malignant tumours) It marks a tumour as malignant because benign neoplasia do not metastasize Metastatic spread strongly reduces the possibility of cure Methods to block metastases would be of great benefit to patients Metastasis Pathways of spread: 1. Direct seeding of body cavities or surfaces: pleural, pericardial and peritoneal cavities 2. Lymphatic spread: secondary tumours in the regional lymph nodes 3. Haematogenous spread (by the blood stream): secondary tumours in organs perfused by blood from a tumour 4. Implantation (after operation): Rare Routes of Metastasis Molecular basis of carcinogenesis ⚫ Non-lethal genetic damage is the basis carcinogenesis ⚫ A tumour is formed by the clonal expansion of a single precursor cell that incurred genetic damage ⚫ Four classes of regulatory genes are the principal targets of genetic damage ⚫ ⚫ ⚫ ⚫ ⚫ The growth promoting oncogenes The growth inhibiting tumour suppressor genes Genes that regulate programmed cell death (apoptosis) Genes involved in DNA repair Carcinogenesis is a multi-step process at both the phenotypic and the genetic levels In lecture test question True or False: Tumour cells always proliferate faster than their normal counterparts. In class MCQ test Which of the following is not for cancer therapy? a) Surgical removal b) Radiotherapy c) Chemotherapy d) Growth hormone therapy e) Immunotherapy Summary Regeneration and stem cells Definitions: Hyperplasia Hypertrophy/ Atrophy Metaplasia Anaplasia Displasia Tumour: Benign versus malignant Nomenclature Metastasis Summary of general pathology Aims of the Module For the student to learn: ⚫ ⚫ ⚫ ⚫ The language of pathology and clinical medicine The principles of general pathology and their application to systematic pathology A basic understanding of the pathogenesis, characteristics and outcomes of examples of diseases The background knowledge of clinical medicine as a basis for biomedical sciences, microbiology (medical) and other related courses Learning outcomes On successful completion, students will be able to: ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ Define the terms for the description of disease Explain the difference between aetiology and risk factors Describe the pathogenesis and characteristics of the major categories of disease Show knowledge of specific organ disorders and the way they affect our body systems Understand pathology and clinical chemistry data for clinical diagnosis Show basic knowledge of key areas of clinical medicine Control of the disease - medical interventions Causes mechanisms Public health Pathological changes Clinical manifestations Complications Clinical medicine Outcomes