DDT.2 Flashcards
(39 cards)
What is cancer?
Cancer is a disease of unregulated growth of cells from genetic mutation. It is a generic term for a large group of diseases that can affect any part of the body.
–> Definition: Malignant, ill-regulated proliferation of cells causing either a solid tumour or other abnormal conditions.
Usually fatal if untreated!
!! Cancer causes death because the cells don’t die instead they populate continuously crowding out healthy cells !!
How are cancer cells abnormal?
1) in the way they multiply indefinitely.
2) how they invade underlying tissue.
3) migrate to other sites of the body and multiply there.
Most common cancer in 2020
Breast cancer
Most deadliest cancer in 2020
Lung cancer
What are the types of cancer?
Carcinomas (cells that cover internal and external body surfaces)
Sarcomas (cells in supportive tissues – bones & muscles)
Leukemia (Blood Cells)
Lymphomas
(Lymph nodes &tissues)
Normal vs Neoplasm
Normal life processes are characterized by continuous growth and maturation of cells, and all cells are subject to control mechanisms that regulate their growth rate.
In contrast, Neoplasm is an overgrowth of cells that serve no useful purpose; for example a tumour.
Classes of tumors: Benign vs Malignant
Growth rate:
slow vs rapid
Character of growth: expansion vs infiltration
Tumor spread:
remains localized vs metastasis in bloodstream and lymphatics
Cell differentiation:
well vs poorly
How are tumors names and classified?
Tumours are named and classified according to the cells and tissues which they originate.
Types of Malignant tumours
Carcinomas
“Malignant tumor from epithelial cells e.g. lung carcinoma, hepatic carcinoma, melanoma”
Sarcomas
“Malignant tumour from connective tissue (osteosarcoma, fibrosarcoma, myosarcoma)”
Lymphoma/Leukemia’s
“Neoplasm of blood cells leukemia, lymphomas, myeloma”
Polyp, papilloma
Any benign tumour projecting from surface epithelium.
Adenoma (adeno- gland )
Benigntumourofepithelial tissue withglandularorigin
-often from glandularorgans, including theadrenal glands,pituitary gland,thyroid,prostate.
Carcinoma
Malignant tumor arising from surface, glandular or parenchymal epithelium (but not endothelium or mesothelium) approx. 90% of human cancers.
Sarcoma
Malignant tumour of any primary tissue other than surface, glandular and parenchymal epithelium.
Leukemia
Neoplasm of blood cells.
What is a teratoma?
“A tumour of mixed cell components”
Often arise in the reproductive tract.
May consist of fat, muscle, bone, hair and oil.
E.g. Dermoid cyct: A common benign cystic teratoma that commonly arises in the ovary”
Oncogenesis
AKA: Tumorigenesis/ carcinogenesis/oncogenesis
Transformation of normal cells into cancer cells entails concerted changes in the expression of many genes.
A single oncogene is insufficient to make normal cells cancerous, whereas cooperation between two distinct oncogenic mutations can BUT in many cases ‘normalizing’ the expression of even one of these genes is sufficient to attenuate tumor growth.
Cancer cell division
Normally, cell divisions are controlled strictly. In cancer cells have lost the capacity to recognize signals from their surroundings. So, the cell number grows out of control;
- They may not detect neighbouring cells.
- They may produce there own growth hormones to stimulate cell division.
- They may not produce tumour suppressor proteins.
- They ignore normal apoptotic processes.
Conventional Oncogenesis Model.
Aging primarily contributes to increased cancers by facilitating the accumulation of oncogenic mutations, including activating mutations in oncogenes or genetic/epigenetic inactivation of tumor suppressor genes.
More than 80% of human cancers being diagnosed after the age of 50, aging represents the single most important prognostic factor for many cancers, including lung, breast, colon, prostate, and certain leukemias.
Therefore, as we age the risk of cancer increases.
This model doesn’t account for all types of cancers so new models are emerging to describe the process….
Adaptive Oncogenesis Model
The ability of an oncogene to induce cancer is context specific.
In a healthy population, the ability of cells to effectively compete for niche space is high due to optimal progenitor cell fitness. Thus, this competition is inherently tumor suppressive.
However, if cellular fitness decreases as a result of aging or environmental insults, the acquisition of an oncogenic mutation could beadaptivedue to its ability to correct or circumvent defective cellular function. In this context, these cells would be selected for leading to carcinogenesis.
Growth of Cancer Cells
Cancer cells can reproduce every 2-6 weeks.
Size of cancer cells:
1M cancer cells = head of a pin
1B cancer cells = a small grape
2^30 = 1 billion cells
Invasion vs Metastasis
Invasion: When cancer cells spread (no longer benign) from the primary site to another part of the body.
Metastasis: Tumor cells are transported through the circulatory system. Transport typically to the bone liver and lungs where they may form secondary/tertiary tumors. Most people who die of cancer die of metastatic disease.
Angiogenesis vs Necrosis
Angiogenesis: as a tumor develops it requires oxygen and nutrients for survival. Cancers often secrete blood vessel stimulators (e.g. VEGF).
Blood vessels grow towards and into tumorgenic masses.
Necrosis: As a tumor enlarges the centre of the tumor may not receive enough nutrients forming a necrotic core.
Skin cancer
To distinguish between a normal mole and a melanoma:
- Asymmetry: when half of the mole does not match the other half.
- Border: when the border of the mole is ragged or irregular.
- Color: when the color of the mole varies throughout.
- Diameter: if the mole’s diameter is larger than a pencil’s eraser.
Nevus
A benign tumor of melanocytes.
