Stomach Cancer: Types and Stages Determine Prognosis

Stomach cancer, also referred to as gastric cancer, is a type of cancer that starts in the stomach. The growth of abnormal cells in the stomach lining causes this cancer. If not treated properly, stomach cancer can spread to other parts of the body such as the liver, pancreas and lymph nodes. 

Before we look at the different types and stages of cancer, let's look at the function and parts of our stomach.

Understanding the Stomach

The stomach is an organ in the human body located between the oesophagus and the large intestine. The stomach acts as a digestive tank that contains gastric juice and enzymes to break down food before it is transferred to the small intestine to absorb nutrients.

The stomach's main components are as follows:

• Cardia: The upper part of the stomach that connects the stomach to the oesophagus
• Fundus: The upper and wider part on the left side of the stomach
• Corpus: The middle part of the stomach
• Antrum: The lower portion of the stomach that connects the stomach to the duodenum 

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Types of Stomach Cancer

Common Stomach Cancer - Adenocarcinoma

The most common form of stomach cancer is adenocarcinoma. It starts in the stomach cells and grows slowly. It usually does not show any early symptoms and only becomes apparent in the later stages.

Here are some risk factors associated with stomach adenocarcinoma:

• Helicobacter pylori (H. pylori) bacterial infection in the stomach
• Cancer of the oesophagus or small intestine
• Consumption of spicy, smoked or salted foods
• Unhealthy eating habits, such as eating fatty and low-fibre foods
• Smoking and excessive alcohol consumption

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Signs and symptoms of stomach adenocarcinoma include:

• Bloating and abdominal pain
• Loss of appetite and unintentional weight loss
• Difficulty swallowing and heartburn
• Nausea and vomiting
• Enlargement of lymph nodes around the stomach

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Rare Stomach Cancer

There are several rare types of stomach cancer. Here are some of them:

1.  Gastrointestinal Stromal Tumour (GIST)

GIST develops from nerve cells in the large intestine wall. It typically grows slowly and is only detected at advanced stages. GIST symptoms and signs include:

• Bloating or abdominal pain
• Having a full stomach despite not eating much
• Vomiting and dizziness

2.  Carcinoid Tumour

Carcinoid tumours are rare and usually harmless types of stomach cancer. It begins in the intestine with cells that produce hormones. Carcinoid tumour signs and symptoms include:

• Abdominal pain and bloating
• Dizziness and vomiting
• Diarrhoea and constipation

3.  Lymphoma

Lymphoma is a type of cancer that begins in lymphatic cells, which are part of the immune system of the body. It rarely affects the stomach, but it can affect the lymph nodes surrounding the stomach. Lymphoma symptoms and signs include:

• Enlargement of lymph nodes throughout the body
• Fever and weakness
• Unintentional weight loss

4.  Squamous Cell Carcinoma

Squamous cell carcinoma is a relatively uncommon type of stomach cancer. It begins in the stomach's surface cells and can spread to other tissues. Squamous cell carcinoma symptoms and signs include:

• Abdominal pain and bloating
• Dizziness and vomiting

5.  Small-Cell Carcinoma

Small-cell carcinoma is a rare type of stomach cancer that typically affects smokers. It originates in the small cells that produce hormones in the stomach. The signs and symptoms of small cell carcinoma include:

• Abdominal pain and bloating
• Feeling full despite eating very little
• Loss of appetite and unintentional weight loss

6.  Leiomyosarcoma

Leiomyosarcoma is a very rare form of stomach cancer that affects the muscle tissue. It usually grows slowly and is only detected at advanced stages. The signs and symptoms of leiomyosarcoma include:

• Abdominal pain and bloating
• Weakness and early satiety
• Unintentional weight loss

TNM Staging System

The TNM staging system is the most commonly used system for evaluating the severity and spread of cancer. TNM is an acronym that stands for Tumour, Node, and Metastasis.

The TNM staging system classifies stomach cancer based on the size of the primary tumour (T), involvement of lymph nodes (N) and spread of cancer (M).

T (Tumour) evaluates the size of the primary tumour in the stomach. There are four T categories in the TNM classification, which are:

• T1: Small tumour that only grows in the inner layer of the stomach (mucosa) or the middle layer of the stomach (submucosa)

• T2: Tumour that grows deeper into the muscle layer of the stomach (muscularis propria)

• T3: Tumour that has spread to the serosa layer or the surrounding tissue

• T4: Tumour that has spread to other organs or structures such as the colon, pancreas, liver or spleen

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N (Node) evaluates the involvement of lymph nodes around the abdomen. There are three N categories in the TNM classification, which are:

• N0: No involvement of lymph nodes

• N1: Regional lymph node involvement

• N2: Distant lymph node involvement

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M (Metastasis) evaluates the spread of cancer to other organs or tissues outside of the stomach. There are two M categories in the TNM classification, which are:

• M0: No spread of cancer to other organs or tissues outside of the stomach

• M1: Spread of cancer to other organs or tissues outside of the stomach

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The Japanese Classification System for Stomach Cancer

The Japanese classification system is a system that Japan uses to assess the severity and spread of stomach cancer. This system classifies stomach cancer based on the size of the primary tumour (T), lymph node involvement (N), and location of the tumour within the stomach. 

Here is a detailed explanation of the Japanese stomach cancer classification:

• T (Tumour) is the same as the TNM classification.

• N (Node) is the same as the TNM classification.

The location of the tumour in the stomach is divided into four categories:

• Tumour located in the upper stomach (cardia and fundus)
• Tumour located in the middle of the stomach (corpus)
• Tumour located in the lower stomach (antrum)
• Tumour spreading throughout the abdomen (penetration)

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The Japanese classification then combines the T category, N category, and location of the gastric tumour into several categories, namely:

• T1: A small tumour that grows only in the inner layer (mucosa) or middle layer (submucosa) of the stomach without involvement of lymph nodes

• T2: A tumour that grows deeper into the muscle layer (muscularis propria) of the stomach without involvement of lymph nodes

• T3: A tumour that has spread to the serosal layer or surrounding tissue with or without involvement of lymph nodes

• T4a: A tumour that has spread to nearby organs or structures such as the colon, pancreas, liver or spleen

• T4b: A tumour that has spread to nearby organs or structures such as the diaphragm, peritoneum or pleura

• N1: Involvement of regional lymph nodes

• N2: Involvement of distant lymph nodes

• P0: No spread of cancer to other organs or tissues outside the stomach

• P1: Spread of cancer to other organs or tissues outside the stomach

The TNM and Japanese classifications of gastric cancer are crucial in determining the appropriate type and strategy of treatment. While the TNM classification is more commonly used in other countries including Malaysia, it is important to consult with a doctor to determine the most suitable classification and treatment strategy for each individual case of stomach cancer.

5 Stages of Stomach Cancer

There are five stages of stomach cancer that are commonly used to assess the cancer's severity and spread.

1.  Stage 0

Stage 0, also known as early gastric cancer, denotes the presence of cancer cells only in the stomach lining. This is considered an early stage because the cancer cells are still confined to their origin and have not spread to other parts of the body.

2.  Stage 1

The condition in which the cancer has grown and spread to the inner layers of the stomach but has not spread to lymph nodes or other organs in the body is referred to as stage 1. The likelihood of recovery at this stage is determined by the location and size of the cancer.

3.  Stage 2

Cancer cells have spread to nearby lymph nodes or the stomach's outer layer in stage 2. Recovery is still possible at this stage, but may be more limited.

4.  Stage 3

Stage 3 has cancer cells that have spread to distant lymph nodes or nearby organs such as the liver or intestines. At this stage, the chances of recovery depend on the type of cancer and the spread of the cancer throughout the body.

5.  Stage 4 

Cancer cells have spread to other parts of the body at this stage, such as the lungs, liver or bones. This stage is typically considered to be very advanced, with very slim chances of recovery.

The Importance of Early Detection

Early detection is crucial in determining the best treatment strategy for patients with stomach cancer. It is important to consult a doctor if you are experiencing symptoms such as difficulty swallowing, persistent stomach pain or sudden weight loss. Remember that early detection increases your chances of beating cancer.

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