Lecture 35 - Neoplasia I
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Neoplasia By Prof. J.T. Anim Department of Pathology
Lecture I
Topics
Nomenclature Definitions Classification of neoplasms Benign vs. malignant neoplasms Characteristics of neoplasms Grading of malignant neoplasms
Neoplasia - Terminology
neo = new, plasia = growth Tumour = swelling Cancer = ‘crab’ Desmoplasia = stimulation of excessive connective tissue (collagen) formation by parenchyma cells
Neoplasia - Nomenclature
Benign neoplasms = ….oma eg. fibroma, lipoma, adenoma (exceptions: melanoma, seminoma, lymphoma) Malignant neoplsms
Mesenchymal: …..sarcoma Epithelial: …..carcinoma
Divergent differentiation of parenchymal cells – mixed tumour eg. pleomorphic adenoma of salivary gland. Neoplasm from more than one germ layer – teratoma
Ectopic rest of normal tissue – choristoma
Aberrant differentiation forming a mass of disorganised but mature specialised cells or tissue indigenous to the particular site - hamartoma
Neoplasia - Definition
Willis
Pitot (1986)
“a neoplasm is an abnormal mass of tissue, the growth of which exceeds and is unco-ordinated with that of the normal tissues, and which persists in the same excessive manner after cessation of the stimulus which has evoked the change” “a tumour is a heritably altered, relatively autonomous growth of tissue”
Summary
“tumours are purposeless growths of tissue that tend to be atypical, autonomous and aggressive”
Neoplasia - Characteristics
Cell proliferation: escape from normal control → immortalisation → most instances, single cell type; numbers inappropriate for anatomical site → tumour
Cell differentiation: impaired differentiation of cell line.
Poor degree of differentiation → worse behaviour of neoplasm. Poor differentiation → acquisition of functional characteristics foreign to differentiated cells eg. foetal proteins etc.
Relationship between cells and surrounding stroma:
Growth in compact mass → benign neoplasm Growth in invasive manner → malignant neoplasm
Neoplasia - Characteristics
Neoplasms are derived from cells that normally maintain a proliferative capacity (mature neurons and cardiac myocytes do not give rise to tumours) A tumour may express varying degrees of differentiation, from relatively mature structures that mimic normal tissues to a collection of cells so primitive that the cell of origin cannot be identified. The stimulus responsible for the uncontrolled proliferation may not be identifiable; it is not known in most human neoplasms. Neoplasia arises from mutations in genes that regulate cell growth, apoptosis or DNA repair.
Neoplasia - Classification
Behaviour (benign vs. malignant)
Histogenetic (tissue of origin)
Combination
Morphological pattern of tumour growth
1. Sessile, polypoid and papillary growth patterns are usually associated with benign tumours.
2. Fungating, ulcerative and annular growth patterns are usually associated with malignant tumours
Neoplasia - Differentiation Impaired differentiation is a feature of dysplasia
Progressive impairment of differentiation leads to carcinoma in situ The undifferentiated cells lose cohesiveness and acquire the ability to invade neighbouring tissues and blood vessels leading to dissemination
Carcinoma in situ: Uterine cervix
Comparison of benign and malignant neoplasms Principal differences in gross morphology of benign and malignant neoplasms
Grading of Malignant Neoplasms
Reflects cellular characteristics Histological and cytological grading are subjective Grade of tumour does not always reflect behaviour – useful guide Determined by the degree of differentiation of neoplastic cells
Low grade neoplasms resemble tissue of origin – evidence of slow growth High grade neoplasms tend to be anaplastic – evidence of rapid growth.
Grading of Malignant Neoplasms
Evidence of rapid or abnormal growth is provided by:
Large numbers of mitoses Atypical mitoses Nuclear and cellular pleomorphism
High N/C ratio Irregular, hyperchromatic nuclei
Presence of tumour giant cells
Low grade urothelial carcinoma
High grade urothelial carcinoma
Anaplastic carcinoma
Anaplasia + abnormal mitoses
Lecture I
Topics
Nomenclature Definitions Classification of neoplasms Benign vs. malignant neoplasms Characteristics of neoplasms Grading of malignant neoplasms
Neoplasia - Terminology
neo = new, plasia = growth Tumour = swelling Cancer = ‘crab’ Desmoplasia = stimulation of excessive connective tissue (collagen) formation by parenchyma cells
Neoplasia - Nomenclature
Benign neoplasms = ….oma eg. fibroma, lipoma, adenoma (exceptions: melanoma, seminoma, lymphoma) Malignant neoplsms
Mesenchymal: …..sarcoma Epithelial: …..carcinoma
Divergent differentiation of parenchymal cells – mixed tumour eg. pleomorphic adenoma of salivary gland. Neoplasm from more than one germ layer – teratoma
Ectopic rest of normal tissue – choristoma
Aberrant differentiation forming a mass of disorganised but mature specialised cells or tissue indigenous to the particular site - hamartoma
Neoplasia - Definition
Willis
Pitot (1986)
“a neoplasm is an abnormal mass of tissue, the growth of which exceeds and is unco-ordinated with that of the normal tissues, and which persists in the same excessive manner after cessation of the stimulus which has evoked the change” “a tumour is a heritably altered, relatively autonomous growth of tissue”
Summary
“tumours are purposeless growths of tissue that tend to be atypical, autonomous and aggressive”
Neoplasia - Characteristics
Cell proliferation: escape from normal control → immortalisation → most instances, single cell type; numbers inappropriate for anatomical site → tumour
Cell differentiation: impaired differentiation of cell line.
Poor degree of differentiation → worse behaviour of neoplasm. Poor differentiation → acquisition of functional characteristics foreign to differentiated cells eg. foetal proteins etc.
Relationship between cells and surrounding stroma:
Growth in compact mass → benign neoplasm Growth in invasive manner → malignant neoplasm
Neoplasia - Characteristics
Neoplasms are derived from cells that normally maintain a proliferative capacity (mature neurons and cardiac myocytes do not give rise to tumours) A tumour may express varying degrees of differentiation, from relatively mature structures that mimic normal tissues to a collection of cells so primitive that the cell of origin cannot be identified. The stimulus responsible for the uncontrolled proliferation may not be identifiable; it is not known in most human neoplasms. Neoplasia arises from mutations in genes that regulate cell growth, apoptosis or DNA repair.
Neoplasia - Classification
Behaviour (benign vs. malignant)
Histogenetic (tissue of origin)
Combination
Morphological pattern of tumour growth
1. Sessile, polypoid and papillary growth patterns are usually associated with benign tumours.
2. Fungating, ulcerative and annular growth patterns are usually associated with malignant tumours
Neoplasia - Differentiation Impaired differentiation is a feature of dysplasia
Progressive impairment of differentiation leads to carcinoma in situ The undifferentiated cells lose cohesiveness and acquire the ability to invade neighbouring tissues and blood vessels leading to dissemination
Carcinoma in situ: Uterine cervix
Comparison of benign and malignant neoplasms Principal differences in gross morphology of benign and malignant neoplasms
Grading of Malignant Neoplasms
Reflects cellular characteristics Histological and cytological grading are subjective Grade of tumour does not always reflect behaviour – useful guide Determined by the degree of differentiation of neoplastic cells
Low grade neoplasms resemble tissue of origin – evidence of slow growth High grade neoplasms tend to be anaplastic – evidence of rapid growth.
Grading of Malignant Neoplasms
Evidence of rapid or abnormal growth is provided by:
Large numbers of mitoses Atypical mitoses Nuclear and cellular pleomorphism
High N/C ratio Irregular, hyperchromatic nuclei
Presence of tumour giant cells
Low grade urothelial carcinoma
High grade urothelial carcinoma
Anaplastic carcinoma
Anaplasia + abnormal mitoses
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