Generality
Colon cancer - or colon cancer or colorectal cancer - is the malignant neoplasm of the large intestine, resulting from the uncontrolled proliferation of one of the cells that make up the wall.
Typical of old age, colon cancer is generally responsible for symptoms such as: changes in bowel habits, rectal bleeding, blood in the stool, anemia, abdominal pain, abdominal cramps, a feeling that the bowel has not emptied after defecation, etc.
Accurate diagnosis of colon cancer requires several investigations; a fundamental diagnostic test is colonoscopy.
Possible treatments for colon cancer include: surgical therapy, radiation therapy, chemotherapy and so-called "targeted therapy".
Brief reference to the anatomy of the intestine
The intestine is the portion of the digestive system between the pylorus and the anal orifice.
The anatomists divide it into two main sectors: the small intestine, also called small intestine, and the large intestine, also called large intestine .
- The small intestine is the first section; it starts at the level of the pyloric valve, which separates it from the stomach, and ends at the level of the ileocecal valve, located on the border of the large intestine. The small intestine consists of three sections (the duodenum, the jejunum and the ileum ), is about 7 meters long and has an average diameter of 4 centimeters.
- The large intestine is the terminal tract of the intestine and of the digestive system. It starts from the ileocecal valve and ends at the anus; consists of 6 sections ( cecum, ascending colon, transverse colon, descending colon, sigma and rectum ), is about 2 meters long and has an average diameter of 7 centimeters (hence the name of large intestine).
| Functions of small intestine and large intestine in short | |
Small intestine | Complete digestion of foods from the stomach and provide nutrient absorption (approximately 90%). |
Large intestine | It absorbs water and electrolytes from what comes from the small intestine and "prepares" feces for expulsion. |
Figure: portions of the large intestine. The large intestine, or large intestine, begins with the portion of the cecum; therefore, it proceeds with the ascending colon, the transverse colon and the descending colon; finally, it ends with the sigma and the rectum. From the histological point of view, the features of the colon, the sigma and the rectum are very similar.
What is colon cancer?
Colon cancer, or colon cancer, is the malignant tumor of the large intestine, the result of the uncontrolled proliferation of one of the cells present in the layers of the inner wall of the large intestine .
In other words, colon cancer is the malignant neoplasm that develops from a "mad cell", located in the inner wall of one of the following traits: ascending colon, transverse colon, descending colon, sigma or rectum.
Clarification on the term "tumor"
The use of the term "colon cancer", to define a malignant tumor of the intestine, is not entirely appropriate (the term "colon cancer" is instead perfect). In medicine, in fact, the word "tumor" means any neoplasm, regardless of its benign or malignant nature.
Nevertheless, in the case of colon cancer - but also of stomach cancer or pancreatic cancer - the use of the word "tumor" is accepted without particular objections, because the latter falls within the common jargon much more than specialized terms, such as for example "adenocarcinoma", "carcinoma", "adenoma" etc.
"Colon cancer" and "colorectal cancer" indicate the same pathology?
In fact, the most correct denominations of the neoplasm described under the names of "colon cancer" or "colon cancer" are others, namely: colorectal cancer, colorectal cancer and colorectal cancer .
However, since colon, sigma and rectum have very similar histological and functional characteristics, it is widely accepted, even by the medical community, the use of the term "colon", instead of "colorectal". Thus, colon cancer, colon cancer, colorectal cancer, colorectal cancer and, finally, colorectal cancer are all to be considered synonymous.
For the most precise ...
"Colorectal cancer" is a rather generic name, which includes three different possible neoplasms of the large intestine: colon cancer, sigmoid cancer and rectal cancer .
Locations typical of colon cancer
The most common localization of colon cancer is the rectum (about 50% of cases), followed by sigma (19-21% of cases), ascending colon (16%), transverse colon (8%) and colon descendant (6% of cases).
Types of colon cancer
There are different types of colon cancer.
Among these types, there is one decidedly more common and important than the others: the so-called colon adenocarcinoma .
Representing 95-97 % of colon cancer cases, this malignant neoplasm originates from the epithelial cells of the mucous membrane of the colorectal tract or from the glands interposed between these epithelial cells.
To complete the picture of the various types of colon cancer (as well as the remaining 3-5% of clinical cases), they are:
- Intestinal lymphoma . Belonging to the category of non-Hodgkin's lymphomas, it is the malignant tumor of the colon that springs from the uncontrolled proliferation of lymphocytes (cells of the immune system) constituting the lymphoid tissue of the intestinal mucosa.
Intestinal lymphoma is also known as intestinal MALToma ; in oncology, MALTomes are the lymphatic system tumors that originate from the lymphocytes of the so-called MALT, ie the Lymphoid Tissue Associated with the Mucosa.
Intestinal lymphoma accounts for 0.5-1% of colon cancer cases.
- Squamous cell carcinoma of the colon-rectum . It is the malignant tumor of the colon-rectal tract resulting from the neoplastic transformation of one of the squamous-type cells, which form the inner lining of the large intestine.
Cancers similar to squamous colorectal cancer can also form in other organs of the digestive system, such as the esophagus.
Colorectal squamous cell carcinoma accounts for about 1% of colorectal cancer cases.
- Gastrointestinal stromal tumor . It belongs to the category of so-called soft tissue sarcomas and originates from one of the particular cells having the function of regulating the motility of food along the digestive tract; cells with this property are found not only in the colon, but in the entire intestine and in the other organs of the digestive system.
Gastrointestinal stromal cancer originating in the colon accounts for less than 1% of colon cancer cases.
- Leiomyosarcoma of the colon or intestinal leiomyosarcoma . Also falling into the category of soft tissue sarcomas, it originates in a smooth muscle cell of the colorectal tract wall.
Colonic leiomyosarcoma accounts for about 1% of colon cancer cases.
- The carcinoid of the colon . It is the malignant neoplasm that originates from one of the colorectal cells with neuroendocrine function. In the human body, cells with neuroendocrine function are hormone-producing cells.
Belonging to the large category of neuroendocrine tumors, the colon carcinoid constitutes just over 1% of colon cancer cases.
What is an adenocarcinoma?
Adenocarcinoma is a particular type of malignant tumor that originates from epithelial cells of the exocrine glandular organs or from epithelial cells of tissues with secretory properties .
Examples of exocrine glandular organs are breast, pancreas or prostate; examples of tissues with secretory properties, on the other hand, are the layers of mucosa that line the inner wall of the airways, esophagus, stomach, colon or rectum.
Adenocarcinomas belong to the large category of carcinomas, malignant tumors that develop from epithelial tissue cells.
Insights
Anatomy and physiology of the colon Causes Intestinal polyps Evaluation of Individual Risk Symptoms and Signs Diagnosis ColonoscopyFemost Blood in Feces Therapy and Prognosis Colectomy Colostomy Diet and Colon CancerCauses
Like most malignant tumors, colon cancer is also an abnormal mass of particularly active cells. This mass derives from a single cell (obviously of the colon) which, due to a series of mutations of its DNA, has acquired the anomalous ability to divide and grow in an uncontrolled way.
Despite the numerous researches conducted so far, the precise causes at the origin of the aforementioned mutations are unknown; however, studies aimed at identifying them have however proved to be useful and important, as they have allowed doctors to decipher, with a good safety margin, the risk conditions (or risk factors) of colon cancer.
Main risk factors
Going into details, the main risk factors for colon cancer are:
- Familiarity with colon cancer . According to experts, people with at least two first-degree relatives affected by colon cancer would be 2 to 3 times more at risk of developing the same cancer, compared to individuals without relatives suffering from colon cancer.
Readers are reminded that familiarity with a tumor only means that, within a family nucleus, more relatives have developed the same neoplasm or a very similar neoplasm.
- The presence of hereditary conditions associated with the development of benign or malignant tumors along the gastrointestinal tract . Scientific studies have shown that those with these inherited conditions present a high risk of developing colon cancer, starting as early as 30-40 years.
The two most well-known and important hereditary conditions associated with the development of tumors along the gastrointestinal tract are: Lynch II syndrome (or hereditary non-polypotic colorectal cancer or HNPCC ) and familial adenomatous polyposis (or FAP ).
Lynch II syndrome is characterized by being the responsible potential for many types of cancer, not just colon cancer; for example, it is capable of causing tumors in the endometrium, stomach, upper urinary tract, ovary, etc.
Familial adenomatous polyposis, on the other hand, is characterized by being the cause of hundreds / thousands of adenomas (or adenomatous polyps ) along the mucosa of the colon-rectal tract of the intestine; colorectal adenomas are benign tumors that have a non-negligible ability to turn into malignant neoplasms.
Readers are reminded that the concept of hereditary predisposition to tumors is different from the concept of familiarity for a tumor: those who have a hereditary predisposition to tumors have, in their own genome, mutations of DNA transmissible from generation to generation, which favor neoplastic processes.
- Inflammatory bowel diseases . These conditions are characterized by chronic inflammation of the large intestine and the consequent alteration of the anatomical structure of the latter.
The two most important inflammatory bowel diseases are ulcerative colitis and Crohn's disease .
Because they are conditions favoring the appearance of colon cancer, doctors advise those who bear it to undergo, periodically, a colonoscopy.
- The presence of adenomatous polyps along the colorectal tract . The ability of adenomatous polyps (which are benign neoplasms) to evolve into malignant tumors has already been discussed, therefore it is not worth repeating.
- An unhealthy diet . Since the entire intestine is a fundamental organ for the transit and expulsion of ingested food, its health is highly dependent on what you eat.
After numerous research and clinical observations, doctors and experts in the field of nutrition have concluded that it is harmful to the colon and favors the appearance of colon-rectal tumors a diet: rich in animal fats, red meat, low in fiber and reduced in fresh fruit and vegetables.
- Advanced age . Generally, the accumulation of mutations underlying tumors such as colon cancer is a slow process, which takes many years. This explains why patients with an intestinal neoplasm are more frequently people over the age of 50.
- Obesity, excessive alcohol consumption, cigarette smoking and a sedentary lifestyle . Statistical studies have shown that obese, large consumers of alcohol, smokers and inactive people, when compared respectively with normal-weight people, abstinent individuals, non-smokers and subjects with an active life, show a greater tendency to develop colorectal cancer.
The precise biological reasons why obesity, excessive alcohol consumption, cigarette smoking and a sedentary lifestyle increase the risk of getting colon cancer are unknown; however, it should be remembered that these risk factors are also included in the list of conditions favoring the formation of adenomatous polyps, along the colorectal tract, and the malignant evolution of such adenomatous polyps.
- Belonging to the African-American race . When compared to other more common breeds (eg, Caucasian or Asian), this breed shows a particular predisposition to colon cancer. The reasons behind this predisposition are unknown.
- Abdominal or pelvic radiotherapy . As it has been known for some time, the ionizing radiations used for radiotherapy treatments represent a factor favoring neoplastic processes.
- Insulin-resistant diabetes . Epidemiological studies have found that, among diabetics with insulin resistance, the number of cases of colon cancer is higher than the number of cases of colon cancer among non-diabetic people.
Based on extremely reliable research, 75-90% of colon cancer cases are not linked to genetic or family risk factors, but to: excessive consumption of red meat, fatty foods and alcohol, cigarette smoking, l obesity, a sedentary lifestyle and the presence of adenomatous polyps.
Epidemiology
Globally, colon cancer represents the second most common form of cancer among women (614, 000 cases; 9.2% of all malignant tumors) and the third most common form of cancer among men (746, 000 cases; 10% of all malignant tumors). It is good, however, to point out that its diffusion varies, sometimes considerably, according to the geographical area considered: for example, in countries like the United States, Australia and New Zealand, colorectal cancer is very more frequently than in African countries.
According to experts, on the difference in the spread of the tumor in question, in various parts of the world, the dietary regime strongly affects: where there is a greater consumption of fatty foods and an insufficient intake of fiber, the incidence values of cancer to the colon they exceed the values of incidence of the same neoplasia in the geographical zones characterized by a low consumption of fatty foods (especially those of animal origin) and / or a diet rich in fibers.
Rare in young adults, colon cancer predominantly affects people over the age of 50-55; statistics in hand, the average age at diagnosis of colorectal cancer is 68 years.
As mentioned, colon malignant tumors have a particular preference for the African-American population.
In recent decades, there has been an interesting phenomenon (and can be explained by the lengthening of life and the improvement of healing techniques): while the incidence of colon cancer has increased, the mortality rate linked to this tumor is decreased.
Epidemiological studies on the incidence of colon cancer among males and females have found that men and women get sick more or less equally.
According to reliable studies, in Italy, every year, colon cancer would be responsible for 40, 000 new cases among women and 70, 000 new cases among men.
Colon cancer in numbers:
- Every year, globally, colon cancer affects more than one million people and causes the death of about 700, 000 sick individuals;
- Worldwide, colorectal cancer is the most common cause of death from cancer, after pulmonary adenocarcinoma (lung cancer), stomach cancer and liver cancer;
- In a country like the United States, colon cancer is the third most common cause of cancer death;
- The American Cancer Society has estimated that, by the end of 2017, in the USA, the new cases of colon cancer will total about 95, 500;
- Colon cancer has the highest incidence rate in Australia and New Zealand and the lowest in West African countries;
- The incidence rate of colon cancer in Afro-American populations is 22-27% higher than the incidence rate of colon cancer in Caucasian populations (27% for males and 22% for females) );
- According to some special studies, individuals born since 1990 present a double risk of getting colon cancer, compared to people born around the 1950s (of the twentieth century of course). The main reason for this change seems to be due to the greater spread of obesity;
- The 5-year survival rate from the diagnosis of stage A colon cancer (the least severe) is over 95%.
The 5-year survival rate from the diagnosis of stage B colon cancer is between 80 and 90%.
The 5-year survival rate from the diagnosis of stage C colon cancer is around 65%.
The 5-year survival rate from the diagnosis of stage D colon cancer (the most severe) is between 5 and 10%.
