Histological subtypes and diagnostics
Primary gastric lymphomas belong to the group of non-Hodgkin lymphomas (NHL). More than 90% of all such lesions are divided in roughly equal proportions into two main histological subtypes:
- Diffuse large B-cell lymphoma (diffuse large B cell lymphoma).
- Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma or MALToma). It is known that the development of this subtype is directly related to mucosal infection by the bacterium Helicobacter pylori.
The main method for confirming the diagnosis is upper endoscopy with biopsy. To assess the extent of the process (detecting extragastric involvement) and subsequently monitor the response to treatment, the gold standard is PET-CT (PET-CT).
Radiological pattern of lymphoma
Imaging studies (using large B-cell NHL as an example) reveal characteristic changes. Computed tomography (CT) shows marked diffuse thickening of the gastric body wall. The mucosa forms so-called giant folds.
FDG-PET (FDG-PET) demonstrates intense radiopharmaceutical uptake in the affected area. Hypermetabolic lymphomatous perigastric lymph nodes are also visualized, indicating regional spread of the tumor process.
Differential diagnosis: Carcinoids
The stomach is the least common site for GI carcinoids; however, they are extremely important clinically due to the risk of associated endocrinopathies. These are well-differentiated endocrine neoplasms of the mucosa and submucosa. Three clinicopathological types are distinguished:
- Type I (most common): Associated with enterochromaffin-like (ECL) cell hyperplasia, hypergastrinemia, and chronic atrophic gastritis (with or without pernicious anemia).
- Type II (least common): Develops against the background of a hypergastrinemic state (Zollinger-Ellison syndrome) in multiple endocrine neoplasia type 1 (MEN 1).
- Type III (sporadic): Not associated with hypergastrinemia. Manifests as large solitary ulcers. It is characterized by an aggressive course, local invasion, and metastases to the liver and lymph nodes.
CT findings for types I and II typically demonstrate small multiple nodules (sometimes with central ulceration) against the background of a diffusely thickened wall. With liver metastases (often in type III), the patient may develop carcinoid syndrome.
Differential diagnosis: Metastatic involvement
Gastric wall metastases are a rare phenomenon characteristic of late-stage oncological processes. Breast cancer, malignant melanoma, and lung cancer metastasize here most frequently.
In early stages, hematogenous metastases radiologically appear as small intramural lesions that are usually multiple and visually indistinguishable from benign lesions. As they progress, they begin to mimic primary tumors: central ulcerations appear within the nodules, forming the specific bull's-eye appearance (bull's-eye appearance). This is particularly typical for metastases of melanoma, lymphoma, and Kaposi sarcoma. Breast cancer can cause diffuse wall thickening—linitis plastica (linitis plastica), which is radiologically indistinguishable from primary carcinoma.
Anatomic aspects and positional anomalies
When evaluating radiological findings, it is important to consider the normal anatomy and mobility of the stomach. It is fixed at the esophagogastric junction and the pyloroduodenal junction, and its mobility is ensured by peritoneal folds: the hepatogastric, gastrosplenic, and gastrocolic ligaments.
The most common anomaly is a hiatal hernia. When the space between the crura of the diaphragm widens, the stomach herniates into the thoracic cavity (occurs in >50% of elderly individuals).
- Sliding hernia (Type 1): The esophagogastric junction is displaced into the thoracic cavity. These hernias are reducible, change size on barium fluoroscopy (especially in the right anterior oblique projection), and are frequently accompanied by gastroesophageal reflux.
- Paraesophageal hernia (Type 2): The junction remains below the diaphragm, while the proximal stomach herniates into the posterior mediastinum. This type is clinically more dangerous due to the propensity for incarceration and obstruction.
Briefly: answers to topical questions
What are the detailed radiological signs of linitis plastica in breast cancer metastases?
The radiological pattern of linitis plastica (linitis plastica) in breast cancer metastases is indistinguishable from primary gastric carcinoma. The following signs are distinguished:
- Fluoroscopy (single contrast) — luminal narrowing due to infiltrative carcinoma involving almost the entire stomach.
- CT (coronal reconstruction) — visualization of tumor infiltration of the body and antrum of the stomach with significant luminal narrowing.
What stages of primary gastric lymphoma are distinguished according to the Lugano classification?
According to the modified Lugano (Lugano) staging system for primary gastrointestinal lymphomas:
- Stage I — disease is confined to the bowel wall.
- Stage II — involvement of draining lymph nodes or adjacent organs.
To remember the causes of bull's-eye gastric ulcerations, use the mnemonic: Melanoma, Lymphoma, Kaposi (sarcoma).
Class and exam questions
What is the main difference between a sliding hernia and a paraesophageal hernia?
In a sliding hiatal hernia, the esophagogastric junction is displaced above the diaphragm, whereas in a paraesophageal hernia, it remains in its normal position while the gastric fundus herniates into the thoracic cavity.
Which method is best suited for assessing lymphoma response to therapy?
PET-CT is the optimal method for monitoring treatment response and searching for extragastric lesions.
How to distinguish type III carcinoid from types I and II?
Type III carcinoid is sporadic, not accompanied by hypergastrinemia, and manifests as large aggressive solitary ulcers, whereas types I and II present as small multiple nodules.
What else to study on this topic
- Pathogenesis of MALT lymphoma development in the setting of H. pylori infection
- Histological structure of gastric B-cell lymphomas
- Zollinger-Ellison syndrome and MEN type 1 in carcinoids
- Radiological signs of linitis plastica
- Mechanisms of incarceration in paraesophageal hernias
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