| Domain | Key points | Key recent sources (URL; publication date) | Evidence citation IDs |
|---|---|---|---|
| Definition/Identifiers | MALT lymphoma is an indolent extranodal marginal zone B-cell lymphoma arising from marginal zone B cells in acquired mucosa-associated lymphoid tissue under chronic antigenic stimulation. It accounts for **>60% of marginal zone lymphomas** and up to **~8% of newly diagnosed lymphomas**. Common primary sites include **stomach (~30–40%)**, **ocular adnexa (~12–24%)**, **skin (~10%)**, **lung (~9–11%)**, and **salivary gland (~7–11%)**. | Raderer et al., *Ther Adv Med Oncol*; https://doi.org/10.1177/17588359231183565; **Jan 2023**. Alderuccio & Lossos, *Expert Rev Hematol*; https://doi.org/10.1080/17474086.2023.2206557; **Apr 2023**. Walewska et al., *Br J Haematol*; https://doi.org/10.1111/bjh.19064; **Nov 2023**. | (pqac-00000000, pqac-00000002, pqac-00000018) |
| Etiology | Strongly linked to chronic inflammation/infection. Gastric disease is associated with **Helicobacter pylori in ~38–85%** of cases; **H. heilmannii <1%**. Other site-specific associations include **Campylobacter jejuni (up to 50%)** in intestinal disease, **Chlamydia psittaci** in ocular adnexal disease (geographically variable), and autoimmune disorders such as **Sjögren syndrome** and **Hashimoto thyroiditis**. HCV is reported in some hepatic/other extranodal cases. | Walewska et al.; https://doi.org/10.1111/bjh.19064; **Nov 2023**. Alderuccio & Lossos; https://doi.org/10.1080/17474086.2023.2206557; **Apr 2023**. Matysiak-Budnik et al.; https://doi.org/10.3390/cancers15153811; **Jul 2023**. | (pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000005, pqac-00000019) |
| Molecular genetics | Recurrent lesions converge on **NF-κB activation**. The translocation **t(11;18)(q21;q21)/BIRC3::MALT1 (API2-MALT1)** is relatively specific and occurs in **~24% of gastric** and **~40% of pulmonary** MALT lymphoma; in gastric disease guideline tables report **~6–26%**. It is associated with more disseminated disease and poor response to H. pylori eradication. Other recurrent abnormalities include **t(14;18)(IGH::MALT1) ~1–5%**, **trisomy 3 ~11%**, **trisomy 18 ~6%**, and **TNFAIP3/A20 inactivation ~5–18%** in gastric MALT. | Raderer et al.; https://doi.org/10.1177/17588359231183565; **Jan 2023**. Walewska et al.; https://doi.org/10.1111/bjh.19064; **Nov 2023**. Yang et al.; https://doi.org/10.1186/s43556-023-00141-3; **Sep 2023**. | (pqac-00000000, pqac-00000001, pqac-00000007, pqac-00000014, pqac-00000015) |
| Diagnostics | Diagnosis is biopsy-based. Recommended gastric workup includes **upper endoscopy with biopsies**; at least **10 biopsies** from lesions and surrounding mucosa are suggested. Histology shows marginal-zone pattern infiltration with **lymphoepithelial lesions**; plasma cell differentiation may be seen in **up to ~33%**. Typical immunophenotype: **CD20+, BCL2+, CD10−, BCL6−, CD5−, cyclin D1−, SOX11−, CD23−, IgD−, usually IgM+**. **FISH for t(11;18)** is recommended in all gastric cases in the BSH guideline. Bone marrow involvement is uncommon (**~4.3%**), so marrow biopsy is not routine unless cytopenias are present. FDG-PET avidity is variable (**~50–60%**). | Matysiak-Budnik et al.; https://doi.org/10.3390/cancers15153811; **Jul 2023**. Walewska et al.; https://doi.org/10.1111/bjh.19064; **Nov 2023**. Alderuccio & Lossos; https://doi.org/10.1080/17474086.2023.2206557; **Apr 2023**. | (pqac-00000014, pqac-00000015, pqac-00000016, pqac-00000017, pqac-00000020) |
| Treatment/outcomes | For early-stage H. pylori-positive gastric MALT, eradication is first-line. A 2023 meta-analysis of **2,936** successfully eradicated H. pylori-positive patients found pooled complete histopathologic remission **75.18% (95% CI 70.45–79.91)**. The 2023 BSH guideline notes **~62% CR by 12 months** after eradication, with late responses up to 1 year. In a 2023 real-world series, CR after eradication in localized H. pylori-positive disease was **77.8% (112/144)**. Radiotherapy for H. pylori-independent/localized disease achieved **100% CR** in H. pylori-negative first-line cohorts in that study; older referenced RT series reported **5- and 10-year OS 94% and 79%**, and the BSH guideline summarizes overall prognosis as **>90% 5-year survival** and **75–80% 10-year survival**. | Lemos et al., *World J Gastroenterol*; https://doi.org/10.3748/wjg.v29.i14.2202; **Apr 2023**. Min et al., *Ann Hematol*; https://doi.org/10.1007/s00277-023-05130-8; **Feb 2023**. Walewska et al.; https://doi.org/10.1111/bjh.19064; **Nov 2023**. | (pqac-00000008, pqac-00000010, pqac-00000011, pqac-00000013) |
| Transformation | Histologic transformation is uncommon but clinically important. In the 2024 prospective cohort/meta-analysis of MZL, pooled cumulative incidence was **~5% at 5 years** and **~8% at 10 years** overall; for **EMZL/MALT**, pooled incidence was about **~3% at 5 years** and **~5% at 10 years**. Transformation was associated with a **3.95-fold increased risk of death**. Reported predictors included **≥2 extranodal sites**, **Ann Arbor stage III/IV**, **elevated LDH**, and **MALT-IPI ≥2**. | Bommier et al., *Blood Advances*; https://doi.org/10.1182/bloodadvances.2024013188; **Nov 2024**. Alderuccio & Lossos; https://doi.org/10.1080/17474086.2023.2206557; **Apr 2023**. | (pqac-00000021, pqac-00000022, pqac-00000023, pqac-00000025) |


*Table: This table summarizes high-yield, evidence-supported facts on MALT lymphoma across definition, etiology, molecular genetics, diagnosis, treatment, and transformation. It prioritizes 2023–2024 sources and includes quantitative findings and context IDs for traceability.*