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Marginal zone lymphomas: what are their mysterious origins?
Marginal zone lymphoma (MZL) is a heterogeneous group of lymphomas arising from the malignant transformation of marginal zone B cells. These B cells are innate lymphocytes that are normally responsible for the rapid production of IgM antibodies in response to antigens, such as those triggered by infectious diseases and damaged tissue. These B cells originate and mature in secondary lymphoid follicles and then migrate to the marginal zone of mucosa-associated lymphoid tissue, spleen, or lymph nodes. According to the World Health Organization (WHO) classification, MZL is divided into three different types: extraepithelial marginal zone lymphoma, splenic marginal zone lymphoma, and nodal marginal zone lymphoma.
Marginal zone lymphoma is generally benign in nature, but its progression may change the severity of the disease.
Extracellular Marginal Zone Lymphoma
Extraepithelial marginal zone lymphoma (EMZL) develops primarily in extraepithelial tissues, especially in the stomach. Approximately 50-70% of EMZL initially present in the stomach, while other rare cases may occur in other organs such as the esophagus, small intestine, and skin. EMZL can be subdivided according to the organs involved. Notably, these lymphomas share similarities in pathophysiological features among different types but differ in clinical presentation, disease progression, and treatment.
PathophysiologyMany factors are involved in the development of EMZL, including a family history of blood cancers, chronic infections, and persistent inflammation caused by autoimmune responses. This chronic inflammation can induce B cells to reorganize their immunoglobulin heavy chains, thereby inducing abnormal cell proliferation and leading to the generation of malignant tumors.
HistopathologyThe malignant transformation of many EMZL patients is closely related to chronic inflammation and infection.
Histopathologic examination of EMZL typically shows cells in a vague nodular or scattered pattern. The malignant cells showed a mixed morphology of small to medium-sized lymphocytes, centrocytes, and large B cells. When large B cells form prominent structures and are separated from other low-grade malignant cells, this may indicate a transition to the more aggressive diffuse large B-cell lymphoma.
Diagnosis, Treatment and Prognosis
The diagnosis of EMZL depends on the organ involved, and most patients are treated in the early stages of symptoms. According to current research, the prognosis of most EMZLs is relatively good, with a five-year overall survival rate ranging from approximately 86% to 95%.
Special Types of Lymphoma
Primary stomach EMZL
Primary gastric EMZL is often associated with Helicobacter pylori infection, with more than 80% of cases being associated with this species. Patients often experience symptoms such as upper abdominal discomfort, nausea, and stomach bleeding. Endoscopic examination can reveal superficial mucosal damage or signs of damage such as ulcers in the stomach. A key aspect of treatment is eradication therapy for H. pylori, which usually consists of a combination of a proton pump inhibitor and antibiotics.
Primary small intestine EMZL
In primary small bowel MZL, patients often face challenges with abdominal pain, diarrhea, and malnutrition. This type of lymphoma is more common in the Mediterranean region and is primarily associated with infection with the foodborne bacterium Campylobacter jejuni. Treatment usually focuses on nutritional support and symptom control.
Other types
EMZL can be divided into multiple subtypes depending on the organ involved, each with specific etiology and prognosis. Developing appropriate treatment options for each subtype is crucial and has a significant impact on the patient's long-term survival prognosis.
The development and associated factors of marginal zone lymphoma in different settings still need to be further studied. Does this mean that we will have a better understanding of its potential dangers and treatment opportunities in the future?
