neoplasia (1 of 6) - كلية الطب · 2020. 1. 22. · neoplasia (1 of 6) introduction = new...
TRANSCRIPT
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Neoplasia (1 of 6)
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Introduction
= new growth
• Oncology = study of neoplasia
• Genetic/epigenetic basis
• Neoplasms are clonal
• Accumulation of mutations…more are accumulated in malignant ones
See next slide
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With accumulation of mutations, features of malignancy are produced • More dysregulated autonomous growth (self-sufficiency in growth signals)
• More lack of response to inhibitory signal
• Evasion of apoptosis
• Limitless replicative potential
• More development of angiogenesis
• Ability to invade surrounding tissues
• Reprograming metabolic pathways
• Evasion of the immune system
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Hamartomas and choristomas
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Well-differentiated Anaplastic
-more N/C ratio -more nuclear pleomorphism -more hyperchromasia -more mitoses -more abnormal mitoses -more large (giant) cells -more bizarre cells -less structures resembling original tissue -more coarse clumped chromatin
What is dysplasia?
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Benign Malignant Less mutations More mutations
Better differentiation (more resemblance to original tissue)
Worse differentiation (less resemblance to original tissue)…more to be anaplastic (anaplasia = total undifferentiation) than benign
Less mitoses More mitoses Mitoses are more likely to be abnormal than in benign
Stroma for supply is present Stroma for supply is also present *Note: some cancers have abundant fibrous stroma (= desmoplasia)
Slower growth…with some exception like? Faster growth
No invasion Invasion
Some with a capsule Mostly no capsule
More circumscribed (well-defined) Less circumscribed (ill-defined)…infiltrative
No metastasis Metastasis
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Metastasis and dissemination
• Basal cell carcinomas…almost always non-metastatic
…also primary tumors of the central nervous system
• Bone sarcomas…usually already spread to lungs at diagnosis
• with differentiation and size…with exceptions
• 3 ways of dissemination
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Metastasis and dissemination, cont’d
• Medulloblastoma or ependymoma…through CSF in ventricles to meningeal surfaces of brain/spinal cord
• Carcinoma…lymphatics, not only through lymphatics
• Sarcoma…blood, not only through blood
• Lung carcinomas regional bronchial lymph nodes tracheobronchial and hilar nodes
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Metastasis and dissemination, cont’d
• Breast:
…usually upper outer quadrant axillary lymph nodes
…medial breast lesions nodes along internal mammary artery
• Sentinel lymph node???
• Enlargement of nodes near cancer are not necessarily involved by the cancer
both may seed supraclavicular or infraclavicular nodes
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Metastasis and dissemination, cont’d
• Veins are penetrated easier than arteries
• The liver and lungs are the most frequently involved secondary sites in hematogenous dissemination
• Vertebral metastases of thyroid and prostate cancers…through the paravertebral plexus
• Renal cell carcinoma…renal vein…may then spread through IVC
• Prostatic carcinoma…bone
• Lung…adrenals and brain
• Neuroblastoma…liver and bones
• Skeletal muscles are rare sites for metastasis
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Epidemiology of cancer Started to decline Cervical cancer deaths markedly
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Epidemiology of cancer, cont’d
• Some geographic areas are with high incidence of smoking & alcoholism
• Dietary fat and fibers colon cancer…differences between the West & Africa
• Death rates from breast cancer are about four to five times higher in the United States and Europe than in Japan
• The death rate for stomach carcinoma in men and women is about seven times higher in Japan than in the United States
• Liver cell carcinoma is relatively infrequent in the United States but is the most lethal cancer among many African populations
• Cervical cancer and its risk factors
Environmental more than genetic
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Epidemiology of cancer, cont’d
• Most cancer deaths occur between ages 55 and 75
• The major lethal cancers in children are leukemias, tumors of the central nervous system, lymphomas, and soft tissue and bone sarcomas
…also retinoblastoma occurs mainly in pediatric age group
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Epidemiology of cancer, cont’d
Occupational hazards
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Epidemiology of cancer, cont’d
Inherited predisposition to cancer
40% of retinoblastoma cases are hereditary
-early age at onset -tumors arising in two or more close relatives of the index case -sometimes multiple or bilateral tumors -not associated with specific marker phenotypes
no more than 5% to 10% of all human cancers fall into one of these three categories
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Epidemiology of cancer, cont’d
• Acquired preneoplastic lesions
…some are due to chronic tissue injury or inflammation
…their removal or reversal may prevent the development of a cancer
…examples: -Squamous metaplasia and dysplasia of the bronchial
mucosa…smokers
-Endometrial hyperplasia
-Leukoplakia of the oral cavity, vulva, or penis
-Adenomas of the colon