Radiological semiotics of lipomas
Gastric lipomas are among rare findings in a radiologist's practice. Traditional barium-contrast X-ray examination of the stomach may show a filling defect, but these radiological signs are extremely non-specific.
Cross-sectional imaging methods are used to reliably verify the process:
- Computed tomography (CT): The classic CT picture presents as a fat-density lesion located in the organ lumen and bounded by a thin capsule.
- Magnetic resonance imaging (MRI): It also allows for the unambiguous determination of the tumor's fatty tissue nature due to specific fat-suppression sequences.
The preferred location for lipomas is considered to be the antrum of the stomach.
Differential diagnosis: mesenchymal neoplasms
When a non-epithelial lesion is detected in the stomach, other mesenchymal tumors must be ruled out, which are divided into two main groups:
- Gastrointestinal stromal tumors (GISTs): This is the most common group of non-epithelial GI neoplasms. A key marker is the overexpression of the KIT receptor (CD117 antigen). The clinical course of GISTs varies widely, and the prognosis depends on three factors: size, location, and mitotic index. The primary imaging modality is contrast-enhanced multidetector CT, which allows for a detailed characterization of the tumor itself, assessment of the extent of its spread, and detection of metastases.
- Non-stromal mesenchymal neoplasms: A group that also includes lipomas. It is characterized by significant heterogeneity and is much less common.
Differential diagnosis: gastric cancer
Malignant gastric lesions in 90–95% of cases are represented by adenocarcinomas (adenocarcinomas). The remaining percentages are distributed among lymphomas, stromal, and neuroendocrine tumors.
Epidemiology and risk factor features:
- The maximum incidence of cancer is recorded in East Asia (where most clinical guidelines have been developed, particularly in Japan) and Latin America.
- The peak incidence occurs at the age of 50–70 years.
- In Western countries, cancer is more often diagnosed at advanced stages due to the non-specificity of early symptoms and the lack of mass screening (in Japan, large-frame fluorography is successfully used for screening).
- Proven risk factors include H. pylori infection, chronic atrophic gastritis, and certain polyposis syndromes. Associated factors include diet and autoimmune gastritis.
- Against the background of H. pylori eradication, the incidence of distal cancer is decreasing, but an alarming increase in proximal cancer among young patients has been noted in the USA.
By location, cancer is distributed evenly: 33% each to the antrum, body, and cardia-fundus zone. About 10% of cases have a diffuse-infiltrative growth pattern.
Concept of early gastric cancer (EGC)
The term early gastric cancer (Early Gastric Cancer - EGC) was proposed by Japanese specialists. It refers to a tumor whose invasion is limited only to the mucosa and submucosa (stage T1), regardless of whether there are lymph node metastases (N status can be any). Patients with EGC often have no symptoms or present with non-specific complaints.
On post-contrast CT images, EGC (e.g., mucosal-restricted Type I) appears as abnormal focal hyperenhancement of the mucosa. At the same time, a preserved outer hypodense strip is visualized — this is the intact submucosa of the organ.
According to the Japanese classification, 3 types of EGC are distinguished, among which:
- Type I (polypoid): the lesion protrudes into the gastric lumen and measures more than 5 mm.
- Type II (superficial): is divided into subtypes (including IIa — elevated).
Briefly: answers to topical questions
What macroscopic types of early gastric cancer (EGC) are distinguished according to the full Japanese classification?
The Japanese classification distinguishes three main macroscopic types of early gastric cancer (EGC):
- Type I (polypoid) — a lesion larger than 5 mm protruding into the gastric lumen.
- Type II (superficial) — subdivided into subtypes IIa (elevated), IIb (flat), and IIc (depressed).
- Type III (ulcerated) — characterized by the presence of a mucosal ulcer defect.
What histological types of malignant epithelial tumors of the stomach are distinguished according to the current WHO classification?
In the general histological classification among malignant epithelial tumors of the stomach, the following nosological variants are distinguished (WHO is not mentioned in the sources).
- Adenocarcinoma (adenocarcinoma) — includes papillary, tubular, and mucinous forms.
- Signet-ring cell carcinoma — consists of cells with intracellular accumulation of mucin-like substances.
- Adenosquamous carcinoma — also referred to as adenoacanthoma.
- Squamous cell carcinoma — rare.
- Undifferentiated carcinoma — includes solid and scirrhous variants.
- Unclassified carcinoma.
To remember the main feature of a lipoma on CT, imagine a nesting doll: inside the 'shell' (thin capsule) is pure fat, the density of which can be easily measured in Hounsfield units.
Class and exam questions
Why is a barium X-ray not enough to confirm a gastric lipoma?
On radiographs, a lipoma yields only a non-specific filling defect. To confirm the fatty structure and the presence of a capsule, CT or MRI is required.
What is the gold standard for evaluating GISTs?
Contrast-enhanced multidetector CT is considered the method of choice, as it allows assessment of the tumor itself, its extent, and the presence of metastases.
Does the diagnosis of 'early gastric cancer' depend on the presence of lymph node metastases?
No. The main criterion for EGC is the depth of invasion (mucosa and submucosa only, T1 stage), while the lymph node status (N) can be any.
What else to study on this topic
- Morphological features of gastrointestinal stromal tumors (GISTs) and CD117 expression.
- Japanese classification of superficial early gastric cancer (EGC Type II and Type III).
- Gastric cancer screening programs: Japan's experience (large-frame fluorography) compared to Western countries.
- Changing epidemiological trends in the incidence of distal and proximal gastric cancer.
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