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Stomach cancer

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Stomach cancer, also known as gastric cancer, is a malignant tumor that develops in the lining of the stomach. This disease occurs when cells grow in an abnormal and uncontrolled way. Most cases of stomach cancer are classified as gastric carcinomas.

Pie chart of stomach cancer types by relative incidence
Pie chart of stomach cancer types by relative incidence

These carcinomas can be divided into several subtypes based on how the cells look under a microscope. The most common type is gastric adenocarcinoma, which begins in the glandular epithelium of the stomach mucosa. Other types include lymphomas and mesenchymal tumors. Understanding these different forms is essential for medical professionals to determine the best course of treatment.

To understand how this cancer progresses, one must look at the mechanism of cell invasion. Adenocarcinomas tend to be aggressive. They start in the lining and then invade the layers of the stomach wall. They move through the muscularis mucosae and the submucosa. Eventually, they can reach the muscularis propria, which is a deeper muscular layer.

Diagram showing the T stages of stomach cancer CRUK 374
Diagram showing the T stages of stomach cancer CRUK 374

If the cancer is not caught early, it may undergo metastasis. This is the process where cancer cells spread from the stomach to distant parts of the body. Common sites for metastasis include the liver, lungs, bones, and lymph nodes.

Diagram showing secondary stomach cancer in the lungs CRUK 186
Diagram showing secondary stomach cancer in the lungs CRUK 186

It can also spread to the lining of the abdomen.

There are distinct ways that these cancers appear. Under the Lauren classification, gastric adenocarcinomas are split into intestinal type and diffuse type. Intestinal-type cells form irregular tubular structures. In contrast, diffuse-type cancers involve cells that do not stick together well. One severe form is linitis plastica, where the cancer invades the entire stomach.

Linitis plastica
Linitis plastica

This can give the stomach a thick, leather bottle-like appearance. Doctors use various tools to see these differences. An endoscopy uses a fiber optic camera to visualize the stomach lining directly.

Por-sig
Por-sig

They may also use endocytoscopy, which provides ultra-high magnification to see cellular structures more clearly.

Research into the causes of stomach cancer has identified several major risk factors. A bacterium called Helicobacter pylori is a primary cause. It is responsible for more than 60% of all stomach cancer cases. The mechanism involves chronic inflammation or the action of specific virulence factors like CagA.

Adenocarcinoma of the stomach
Adenocarcinoma of the stomach

Other risks include smoking, which can increase the risk by 40% to 82% depending on how heavily a person smokes. Obesity is also a factor. It may increase the risk of gastric cardia adenocarcinoma by more than two times. This is often linked to gastroesophageal reflux disease, or GERD. Dietary habits also play a role, as foods like pickled vegetables are associated with higher risk.

Genetics also play a significant part in some cases. About 10% of stomach cancer cases run in families. Between 1% and 3% of cases are caused by inherited genetic syndromes. One specific example is hereditary diffuse gastric cancer, or HDGC. This is caused by a mutation in the CDH1 gene located on the 16th chromosome. This gene codes for a protein called E-cadherin. This mutation is considered autosomal dominant. This means half of the children of a carrier will likely inherit the same mutation. Families with a history of cancer diagnosed before age 50 are often monitored closely.

Diagnosis is a multi-step process used to confirm the presence of cancer. The most important step is a biopsy. During an endoscopy, a doctor takes a small piece of tissue. This tissue is sent to a pathologist for histological examination. This is the only sure way to confirm cancer cells are present. Doctors may also use medical imaging like CT scans to see if the cancer has spread. In 2013, scientists reported a successful pilot study using a breathalyzer-style test. This test analyzes chemicals in exhaled breath to help diagnose the disease without an invasive procedure.

Stomach cancer is a major global health issue. It is the fifth-leading type of cancer and the third-leading cause of cancer death worldwide. In 2018, it occurred in 1.03 million people and caused 783,000 deaths. It makes up 7% of all cancer cases and 9% of cancer deaths. The impact varies greatly by region. In the United States, the five-year survival rate is 37.9%. However, in South Korea, it is over 65%, and in Japan, it is over 70%. These higher rates in East Asia are partly due to regular screening efforts. Historically, rates declined in the West as refrigeration reduced the need for salted and pickled foods.

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🖼️ Images & Media (10)
File:Por-sig.jpg
Por-sig.jpg
File:Linitis plastica.jpg
Linitis plastica.jpg
File:Adenocarcinoma of the stomach.jpg
Adenocarcinoma of the stomach.jpg
File:Pie chart of stomach cancer types by relative incidence.png
Pie chart of stomach cancer types by...
File:Diagram showing the T stages of stomach cancer CRUK 374.svg
Diagram showing the T stages of stomach...
File:Diagram showing secondary stomach cancer in the lungs CRUK 186.svg
Diagram showing secondary stomach cancer...
File:Infiltrative (poorly cohesive) gastric cancer.jpg
Infiltrative (poorly cohesive) gastric cancer.jpg
File:Infiltrative gastric cancer showing thickened stomach wall.jpg
Infiltrative gastric cancer showing...
File:Diagam showing the anatomy before Roux-en-y surgery for stomach cancer CRUK 002.svg
Diagam showing the anatomy before...
File:Stomach cancer world map-Deaths per million persons-WHO2012.svg
Stomach cancer world map-Deaths per...
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