Neoplasia

NEOPLASIA (I)
1. DEFINITIONS:
NEOPLASIA: ‘new growth’ it refers to the process of uncontrolled proliferation of cells in a tissue or an organ which results in the formation of a NEOPLASMA.
There are two types of NEOPLASMS, those that cannot form solid masses causing intraepithelial cervical neoplasia and leukemia, and those that form solid masses, called as TUMORS.
Talking about tumors wecan say that there are two different types: benign and malignant
Both of them have two basic components, the first one is the parenchyma, which is proliferating neoplastic cells, and the second one is the stroma, which is formed by connective tissue and blood vessels.
Benign is a tumor that lacks the ability to metastasize, so it lacks the invasive properties of a cancer. The term implies amild and non-progressive disease.
Some examples: adenomas, papillomas, polyp,etc.
Malignant tumors also known as cancers, they have their own characteristics which are:
* They proliferate with autonomy: without following natural laws of cell proliferation.
* Monoclonality: all members of the tumor cells belong to a single clone because they come from a mutated cell.
* Anaplasia: theyare less differentiated than the normal equivalent ones.
* Agressivity: tumor cells invade and destroy nearby structures and develop metastasis or distant sources, for which are carried by the blood and linfa.
* Fast growth
Finally we can classify tumors as mixed tumors: they can develop benign or malign tumors.
ONCOLOGY: is the science which studies tumors and neoplasias.
ONCOGENESISOR CARCINOGENESIS: is the creation of cancer. It is a process by which normal cells are transformed into cancer cells.
Carcinogenic factors, which cause damage in the DNA:
* Chemical agents:
* Physical agents: radiations;
* Biological agents: virus, bacteria, fungi, parasites…
* Herency
* Other factors: diet, age…

2. Oncogenesis or carcinogenesis: is the creationof cancer. It is a process by which normal cells are transformed into cancer cells. This process is characterized by a progression of changes on cellular and genetic level, which will reprogram the cell to undergo uncontrolled cell division, and in consequence forming a malignant tumor.
This process is caused by the mutation of the normal cell’s genetic material, which will cause an abnormalequilibrium between proliferation and cell death, resulting in an uncontrolled cell division.
In fact, it is necessary several mutations in certain types of genes before the transformation of a normal cell into a cancer cell occur. Only mutations in those genes that play vital roles in cell division, apoptosis and DNA repair, will lose the control of its cell proliferation.
Those genes are:
*Oncogenes result from mutation of proto-oncogenes, which encode the production of proteins involved in growth control.
* Cancer suppressor genes (GSC) or antioncogenes whose absence (not their presence as in the case of oncogenes) is responsible for the development of cancer, those genes produce the synthesis of products that stop the growth and cell proliferation. For example: the p53 gen thatactivates the DNA repair enzymes to correct the detected damage.
Activation of a proto-oncogene, and therefore its transformation to an oncogene results from mutations caused by:
* Physical causes (ionizing radiation)
* Chemical causes (carcinogens)
* Biological causes (oncogenic viruses)
* Transmitted by heredity mutations over generations.
* Failures in any of the DNA repairmechanisms.
Mechanisms for the activation of oncogenes are:
1. Point mutations
2. Gene amplification
3. Chromosomal translocation
4. Deletion of genetic material

3. TUMORS’ BIOLOGY

4.1 - GROWING OF TUMOR:
The process of development of most malign tumors can be divided in 4phases:
1. Transformation: normal cells mutate into tumor cells dividing out of control....