The gastrointestinal tract (GIT) comprises several organs that digest and absorb food and excrete waste metabolites. The gastrointestinal tract comprises the esophagus, stomach, small intestine, large intestine, colon, rectum, and anus. Other organs that help digest food include the liver and pancreas.
Different GIT organs have different types of cells, including mucus-secreting cells, glandular cells, neuroendocrine cells, and epithelial cells, and these play a pivotal role in the optimum functioning of the different gastrointestinal tract organs.
Due to mutations in one or more cells of the gastrointestinal tract, the cells divide without any control, resulting in the formation of a tumor. If not diagnosed and treated early, the tumor may spread to other organs of the gastrointestinal tract, lymph nodes, or nearby and distant organs, such as the lungs or bones.
Primary GIT cancer starts in the GIT, while metastatic GIT cancer forms in other organs and spreads to one or more organs of the GIT.
Gastrointestinal carcinoma is one of the most common cancers. Despite the advancements in the diagnosis and management of GIT cancer, it is still one of the most common reasons for cancer-related deaths. Different types of gastrointestinal tumors have different incidence rates. Although there are reports of a reduction in the incidence of some types of gastrointestinal cancers, these cancers pose a healthcare challenge.
Based on the organs that they arise from, GI cancers are categorized into various types. The following are the different types of gastrointestinal tumors:
Colorectal cancer is the term used for colon and rectal cancer. Based on the initiation site, these cancers may be subdivided into colon or rectal cancers. The early stage of colorectal cancer is the presence of polyps in the rectum or colon.
The esophagus is a long tube carrying food from the oral cavity to the stomach. Esophageal cancer in most patients is diagnosed at an advanced stage as it does not cause symptoms or the symptoms overlap with other common conditions.
Stomach or gastric cancer starts in the stomach. The cancer may develop in any part of the stomach. Although there has been a significant reduction in the incidence of stomach cancer in the past couple of decades, it is still one of the most common cancers.
The pancreas is an organ located behind the stomach that assists digestion by releasing pancreatic fluid. It also releases hormones that regulate blood sugar. Uncontrolled growth of pancreatic cells results in pancreatic cancer.
The anal canal is situated at the end of the rectum, through which the stool or fecal matter is excreted from the body. Anal cancer occurs due to the uncontrolled division and proliferation of anal cells. Patients with anal cancer present with anal pain, itching, and rectal bleeding.
The liver is the body's largest internal organ and performs several essential functions. Various types of cells are present in the liver. Uncontrolled division and proliferation of one or more of these cells result in liver cancer.
The development of malignant cells in the small intestine results in small intestinal cancer. The condition is also called small bowel cancer. Small intestinal cancer is uncommon and constitutes about 3% of all gastrointestinal cancers.
Gastrointestinal cancer staging is done to evaluate the extent of the disease’s spread. The staging parameters may slightly vary for different types of gastrointestinal cancer. In general, the following are the important gastrointestinal cancer stages:
It is known as carcinoma in situ. This stage suggests the presence of abnormal cells on the mucosal layer. These cells can potentially develop into cancer and spread to nearby healthy tissues.
This stage is categorized into stages IA and IB. In stage IA,
cancer develops in the mucosa and may have spread to the submucosa.
In stage IB, cancer has developed in the mucosa and invaded the muscle tissues; in stage; OR cancer has developed into the mucosa, spread to the submucosa, and invaded 1–2 nearby lymph nodes.
In stage IIA, the cancer cells invade the submucosa and 3 to 6
nearby lymph nodes; OR cancer affects the muscle layer, and 1 to 2 nearby lymph
nodes; OR cancer invades the subserosa.
In stage IIB, cancer cells invade the submucosa and 7 to 15 nearby lymph nodes; OR cancer affects the muscle layer, and 3 to 6 nearby lymph nodes; OR cancer invades the serosa.
In stage IIIA, the muscle layer is invaded along with 7 to 15
nearby lymph nodes; OR subserosa and 3 to 6 nearby lymph nodes; OR serosa and 1
nearby lymph nodes; OR cancer spreads to surrounding organs, such as the
liver, and pancreas.
In stage IIIB, cancer invades the muscle layer and 16 or more nearby lymph nodes; OR serosa or submucosa and 7 to 15 nearby lymph nodes; OR nearby organs; and 1 to 6 nearby lymph nodes.
In stage IIIC, cancer spreads to the serosa or subserosa and ≥16 nearby lymph nodes; OR surrounding organs and seven or more nearby lymph nodes.
Gastrointestinal cancer stage 4 is also known as advanced or metastatic cancer. In this stage, cancer metastasizes to distant organs, such as the liver, lungs, and distant lymph nodes.
Gastrointestinal cancer develops in the gastrointestinal tract, which includes the esophagus, small intestine, stomach, large intestine, colon, rectum, and anus. It also includes cancers of the liver and pancreas. The staging of gastrointestinal cancer is done to understand how far the disease has spread. Stages I and II refer to the early stages of GI cancer, whereas stage IV is the most advanced stage of gastrointestinal cancer.