The risk factors are mentioned below:

• Family history of colon cancer.
• Chronic diseases of the intestine(like inflammation of intestine).
• A regular diet with low fibers but high calories.
• Diabetes.
• Obesity.
• Consuming high amount of alcohol.

Colorectal cancer is a term used to refer to cancer that develops in the colon or the rectum. The colon and rectum are parts of the digestive system.The first and major part of the large bowel, i.e. the colon, continues to absorb water and mineral nutrients from the food matter and serves as a storage place for waste matter. The waste matter left after this process is feces and goes into the rectum, the final 6 inches of the large bowel. From here it passes out of the body through the anus.

The colon has four sections:

• The first section is called the ascending colon.
• The second section is called transverse colon.
• The third colon is called descending colon.
• The fourth part is called the sigmoid colon. The sigmoid colon joins the rectum, which in turn joins the anus, or the opening where waste matter passes out of the body.

The walls of each of these sections of the colon and the rectum have several layers of tissue. Colorectal cancer starts in the innermost layer and can grow through some or all of the other layers. In most people Colo-rectal cancers develop slowly over a period of several years. Before the symptoms can be felt. A vast majority of colo-rectal cancers are adenocarcinoma. These are cancers of the glandular cells that line the inside layer of the wall of the colon and rectum.Carcinoid tumors develop from specialized hormone producing cells of the intestine.Gastrointestinal stromal tumors develop from specialized cells in the walls of the colon called the ‘interstitial cells of the cajal’.Some tumors are benign, others are malignant (cancerous). Although these cancers can be found anywhere in the gastrointestinal tract, they are unusual in the colon.

STOMACH CANCER

The stomach is a sack like organ that holds food and begins the digestive process by secreting gastric juices. The food and gastric juice are mixed and then emptied into the first part of the small intestine called the duodenum.

The stomach is divided into five sections. The upper portion (closest to the esophagus) is the proximal stomach. Some cells of this area of the stomach produce acid and pepsin ( a digestive enzyme), the ingredients of the gastric juice that helps digest food. The lower portion is the distal stomach. This area includes the antrum, where the food is mixed with gastric juices, and the pylorus, which acts as a valve to control emptying of the stomach contents into the small intestine. Other organs next to the stomach include the colon, liver, spleen, small intestine, and pancreas.

The stomach has five layers. The innermost layer is called mucosa, in mucosa stomach acid and the digestive enzymes are made. Next layer is called submucosa. Submucosa is surrounded by muscularis, a layer of muscle that moves and mixes the stomach contents.

The next two layers, the submucosa and outermost serosa act as wrapping layers for the stomach. Most stomach cancers start in the mucosa. Stomach cancers develop slowly over many years. Stomach cancers can spread or metastasize, in different ways. They can grow through the walls of the stomach and eventually grow into the nearby organs. They can also spread to the lymph nodes. Of cancer spreads to the lymph nodes the chances of cure also becomes less. In later stages the stomach cancer will travel through the bloodstream and form metastasis in organs such as liver, lungs, and bones. Even if it has spread to other organs it is still called stomach cancer.

Majority of stomach cancers are adenocarcinoma. They develop from the epithelial cells that form the epithelial cells that form the innermost lining of the stomach’s mucosa.

The other less frequently occurring cancers of the stomach are:

• Lymphoma.
• Gastrointestinal stromal tumors.
• Carcinoid tumors .

Risk factors:

• Age: Most cases of stomach cancers can occur in people over age 55.
• Gender: Men have double the risk of developing stomach cancer as compared to women.
• Family history: People who have a first degree relative who has had stomach cancer are at an increased risk for stomach cancer.
• Diet: Consuming foods preserved with preservatives can increase the risk of developing stomach cancer. Eating fresh fruits and vegetables can reduce the risk of developing stomach cancer..
• Bacteria: A type of bacteria called H-pylori, which causes stomach inflammation and ulcers, may increase the risk of stomach cancers. However most people infected with this disease never develop stomach cancer.
• Previous surgery or health conditions: People who have had stomach surgery or pernicious anemia (severe decrease in red blood cells) or achlorhydria (absence of hydrochloric acid in the gastric juices) which helps digest food have an increased risk of stomach cancers.
• Occupational exposure: Exposure to certain dusts and fumes may increase the risk of developing stomach cancer.
• Obesity: - Excess body weight increases the risk for stomach cancer.

Signs & Symptoms:

• Indigestion or heartburn.
• Pain or discomfort in the abdomen.
• Nausea and vomiting.
• Diarrhea or constipation.
• Bloating of the stomach after meals.
• Loss of appetite.
• Weakness and fatigue.
• Vomiting blood or having blood in the stool.
• Unintended weight loss.

These symptoms can also be caused by many other illnesses, such as a stomach virus or an ulcer.