The following genes take part in the cancer:
- Oncogenes – these are cancer causing genes. They may be normal genes which are expressed at inappropriately high levels in patients with cancers or they may be altered or changed normal genes due to mutation. In both cases these genes lead to cancerous changes in the tissues.
- Tumor suppressor genes – these genes normally inhibit cell division and prevent survival of cells that have damaged DNA. In patients with cancer these tumor suppressor genes are often disabled. This is caused by cancer-promoting genetic changes. Typically, changes in many genes are required to transform a normal cell into a cancer cell.
Sometimes there may be genomic amplification. Here a cell gains many copies (often 20 or more) of a small chromosomal locus, usually containing one or more oncogenes and adjacent genetic material.
Point mutations occur at single nucleotides. There may be deletions, and insertions especially at the promoter region of the gene. This changes the protein coded for by the particular gene. Disruption of a single gene may also result from integration of genomic material from a DNA virus or retrovirus. This may lead to formation of Oncogenes.
Translocation is yet another process when two separate chromosomal regions become abnormally fused, often at a characteristic location. A common example is Philadelphia chromosome, or translocation of chromosomes 9 and 22, which occurs in chronic myelogenous leukaemia, and results in production of the BCR-abl fusion protein, an oncogenic tyrosine kinase.
A tumor in latin means a swelling but not all swellings are tumors in the modern sense of the term. Some of them may be caused due to inflammation, infections, cysts or fluid filled lesions or due to benign growths. A cancerous tumor has the capacity to grow rapidly and to metastasize or spread to other tissues. Some tumors like leukemias grow as cell suspensions but most grow as solid masses of tissue.
Solid tumor parts
Solid tumors have two distinct parts. One of them is the parenchyma that contains cancer tissues and cells and the other is the stroma that the neoplastic cells induce and in which they are dispersed.
Structure of cells:
- Hyperplasia occurs when cells within a tissue multiply faster than normal and extra cells build up. However, the cells and the way the tissue is organized still look normal under a microscope. Hyperplasia can be caused by several factors or conditions, including chronic irritation.
- Dysplasia is a more advanced condition than hyperplasia. In dysplasia, there is also a buildup of extra cells. But the cells look abnormal and there are changes in how the tissue is organized. In general, the more abnormal the cells and tissue look, the greater the chance that cancer will form. Some types of dysplasia may need to be monitored or treated, but others do not. An example of dysplasia is an abnormal mole (called a dysplastic naevus) that forms on the skin. A dysplastic nevus can turn into melanoma, although most do not.
- Carcinoma in situ is an even more advanced condition. Although it is sometimes called stage 0 cancer, it is not cancer because the abnormal cells do not invade nearby tissue the way that cancer cells do. But because some carcinomas in situ may become cancer, they are usually treated.