MALToma

MALTomas develop from chronic antigenic stimulation of mucosal lymphoid tissue, leading to clonal proliferation of marginal zone B-cells. The classic example is gastric MALToma caused by chronic H. pylori infection, which induces lymphoid tissue formation in the stomach (normally lacking organized lymphoid tissue) through sustained immune activation. Key genetic associations include t(11;18)(q21;q21) causing API2-MALT1 fusion, and t(14;18)(q32;q21) involving IGH-MALT1, both leading to NF-κB pathway activation that promotes lymphocyte survival and proliferation. Clinically, patients may present with dyspepsia, abdominal pain, or be asymptomatic with incidental discovery on endoscopy. Diagnosis involves endoscopic biopsy showing lymphoepithelial lesions with marginal zone B-cells infiltrating gastric glands. A critical board-relevant point is that early-stage gastric MALToma (localized, H. pylori-positive) often regresses with H. pylori eradication therapy alone (triple therapy: PPI + amoxicillin + clarithromycin), avoiding the need for chemotherapy or surgery in many cases. This exemplifies how treating the underlying antigenic stimulus can resolve a lymphoid malignancy, a unique therapeutic concept in oncology. If the translocation t(11;18) is present, tumors are typically less responsive to H. pylori eradication and may require additional therapy. Other MALToma sites include salivary glands (associated with Sjögren syndrome), thyroid (associated with Hashimoto thyroiditis), lung, and ocular adnexa. Extragastric MALTomas are also linked to chronic antigenic stimulation but may require different first-line therapies such as radiation or rituximab. MALTomas generally have an indolent clinical course but can rarely transform into diffuse large B-cell lymphoma (DLBCL). This topic frequently tests understanding of the relationship between chronic inflammation/infection and lymphomagenesis, as well as the unique treatment paradigm of antibiotic-mediated tumor regression.