What Is GIST? Gastrointestinal Stromal Tumour Symptoms, Causes & Types

Have you come across the term GIST in a medical report or heard your doctor mention a gastrointestinal stromal tumour? It is normal to have questions about what it means and whether it is a form of cancer.

A gastrointestinal stromal tumour (GIST) is a rare type of tumour that develops in the wall of the digestive tract, most commonly in the stomach or small intestine. It originates from specialised cells involved in controlling digestive movement. While some GISTs grow slowly, others can behave aggressively and spread to other parts of the body.

GIST is different from common stomach and intestinal cancers because it develops from supporting tissues rather than the inner lining of the digestive tract.

Let’s understand what a GIST tumour is, why it develops, its symptoms and how it differs from other gastrointestinal cancers.

What Does GIST Stand For?

GIST stands for Gastrointestinal Stromal Tumour.

The name describes the type and location of the tumour:

• Gastrointestinal: Relates to the digestive system, including the stomach and intestines.

• Stromal: Refers to supporting tissues within an organ.

• Tumour: An abnormal growth of cells.

GIST develops from specialised cells called interstitial cells of Cajal (ICCs) or their precursor cells. These cells act like natural pacemakers of the digestive tract, helping coordinate the muscular contractions that move food through the stomach and intestines.

When genetic changes affect these cells, they may start multiplying uncontrollably and form a tumour.

Where Do GIST Tumours Develop?

GIST can develop anywhere along the gastrointestinal tract, from the oesophagus to the rectum. However, some locations are more common than others.

The stomach is the most frequent site, accounting for approximately 50–60% of cases. The small intestine is the second most common location.

Other possible locations include:

• Stomach: The most common site of gastrointestinal stromal tumours.

• Small intestine: GISTs can develop in the duodenum, jejunum or ileum.

• Colon and rectum: Less common locations.

• Oesophagus: GIST in the oesophagus is relatively rare.

The location matters because it can influence how the tumour behaves and how doctors evaluate it.

What Causes GIST Tumours?

Most GIST tumours develop due to genetic mutations that cause certain cells in the digestive tract to grow and divide abnormally.

Two genes are particularly associated with GIST:

1. KIT Gene Mutations

The KIT gene provides instructions for producing a protein that helps regulate cell growth and survival.

In many GIST cases, a mutation causes the KIT protein to remain switched on, sending continuous signals that encourage cells to multiply.

2. PDGFRA Gene Mutations

The PDGFRA gene produces another receptor protein involved in cell growth.

Changes in this gene can also lead to abnormal cell multiplication and tumour formation.

Most GIST-related genetic mutations are acquired during a person’s lifetime. This means they develop in the cells over time rather than being inherited from parents.

Rarely, GIST may run in families due to inherited genetic conditions, such as familial GIST syndrome or certain cases associated with neurofibromatosis type 1.

Can lifestyle cause GIST?

There is currently no established evidence that a particular food, eating habit or common lifestyle factor directly causes most GISTs. The condition is primarily associated with genetic changes in the affected cells.

What Are the Symptoms of GIST?

One reason GIST can go unnoticed is that small tumours may not cause any symptoms. They are sometimes discovered accidentally during an ultrasound, CT scan or endoscopic examination performed for another reason.

When symptoms develop, they may include:

• Persistent abdominal pain or discomfort.

• Blood in the stool or black, tarry stools.

• Vomiting blood.

• Unexplained anaemia and fatigue.

• Feeling full after eating a small amount of food.

• Abdominal swelling or a lump.

• Nausea and vomiting.

These symptoms depend partly on the tumour’s size and location. For example, a tumour that bleeds into the digestive tract may cause anaemia, while a larger tumour may cause abdominal discomfort.

It is important to remember that these symptoms do not automatically indicate GIST. Several digestive conditions can cause similar problems.

Is GIST the Same as Stomach Cancer?

No. GIST and conventional stomach cancer are two different conditions, even though both can develop in the stomach.

The main difference is where the tumour originates.

Stomach cancer, particularly adenocarcinoma, develops from the cells lining the stomach. A GIST develops from specialised supporting cells within the gastrointestinal wall.

Here are some important differences:

This distinction is important because the two conditions have different biological characteristics and require different treatment approaches.

Is Every GIST Tumour Cancerous?

Not every GIST behaves aggressively.

Some GISTs have a very low risk of spreading, while others can grow into malignant tumours and spread to distant organs.

Doctors evaluate several characteristics to understand how a particular GIST may behave:

• Tumour size: Larger tumours generally carry a higher risk of aggressive behaviour.

• Mitotic rate: This measures how quickly tumour cells are dividing. A higher rate may indicate more aggressive growth.

• Tumour location: Gastric and non-gastric GISTs can have different risk profiles.

• Tumour rupture: Rupture can increase the risk of recurrence and spread within the abdomen.

Therefore, the word GIST alone does not tell you how serious a particular tumour is. Its individual characteristics need to be evaluated.

How Is GIST Identified?

GIST may first be suspected when an imaging test or endoscopic examination reveals an unusual growth in the gastrointestinal wall.

Doctors use specialised investigations to determine whether the growth is actually a GIST or another type of tumour.

A few important terms you may encounter in a medical report include:

• CD117 (KIT): A protein commonly found in GIST cells and an important diagnostic marker.

• DOG1: Another marker used to help identify GIST.

• Immunohistochemistry (IHC): A laboratory technique that checks for specific proteins in tumour tissue.

• Molecular testing: Identifies genetic changes such as KIT and PDGFRA mutations.

These findings help specialists understand the nature of the tumour and distinguish it from other gastrointestinal growths.

Understanding a GIST Diagnosis

Being diagnosed with a gastrointestinal stromal tumour can raise many questions. However, the term GIST alone does not determine how serious the condition is. The tumour’s location, size, genetic characteristics and biological behaviour all matter.

An accurate diagnosis and specialist evaluation help determine the appropriate next steps.

For patients diagnosed with GIST, Dr. Deep Goel provides specialist evaluation and gastrointestinal tumour care in Delhi. To understand the available treatment approaches, read more about Gastrointestinal Stromal Tumours Treatment in Delhi.