What is a tumour?
Cancer nowadays is considered a pathology with a genetic component that occurs when cellular growth is out of control. Our body cells receive signals telling them when to grow and multiply and when such growth must stop. In a tumour, such cells do not respond to control signals and grow and multiply abnormally, spreading to different parts of the body, due to changes in their DNA.
The event leading to the alteration of genetic functions is called “mutation”. When a gene is affected by mutation for different causes (biological, chemical and physical), information to the cell will not be adequate for its functions.
Is cancer hereditary?
Neoplasms are mostly pathologies caused by multiple factors generated by
genetic and environmental risk factors. Most tumours are “sporadic”, that is,
they arise in the general population without any clear signs of a genetic
susceptibility. In these types of tumours, DNA alterations (mutations) randomly
develop in somatic cells, namely, those cells creating every organ and system of
our body. These mutations develop in the DNA of a small group of cells and
generate the genetic error that is perpetrated in the descendants of those
cells. After having accumulated in an organ, they initially replace the healthy
cells of that organ and then spread to other organs, both nearby and distant
(metastasis).
There are forms of tumour called "familial", when people
affected by cancer in the family are close relatives. Cancer familiarity is a
significant risk factor, especially when common environmental risk factors are
also shared (lifestyles, diet, polluting agents, etc.) without a specific
genetic alteration that makes the subject more susceptible to the disease.
Only a small, but significant, percentage of tumours are “hereditary”. Estimates
say that around 5-10% of breast cancers and 10-25% of ovarian cancers have a
hereditary component. In these tumours, DNA mutations occur in germ or
reproductive cell and, therefore, may be passed on to the person's offspring. At
birth, the child will show the genetic defect in one or more genes in all cells
of the body and, therefore, will be susceptible to the development of a neoplasm
when, during his/her life, other mutations occur.
When a new person is
conceived, s/he acquires two pairs of each gene, one pair from the father and
one from the mother. Any genetic mutations in the DNA of the parents are,
therefore, passed on to children. If one of the parents has a mutation in one of
the cancer-generating genes (hereditary tumour), the offspring has a 50% chance
of inheriting that mutation. People inheriting a germ cell mutation are born
with a copy of the mutated gene. These people do not inherit the tumour, but
only the susceptibility to develop that type of cancer more easily, compared to
the general population.