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Case Report: pulmonary MALT lymphoma with BIRC3::MALT1 fusion and indeterminate PET/CT findings
1Department of Geriatrics, Xiangyang No.1 People's Hospital, Hubei University of Medicine, Xiangyang, China.
Background:
Pulmonary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (pulmonary MALT lymphoma) is an indolent B-cell lymphoma that can mimic infection, inflammatory disease, or epithelial malignancy. Indeterminate fluorodeoxyglucose-avid abnormalities may complicate staging and lead to overinterpretation of disease extent.
Case Presentation:
A 49-year-old man with no smoking history underwent video-assisted thoracoscopic right lower-lobe superior segmentectomy for a 12 × 9 mm pulmonary nodule. Histopathology and immunohistochemistry supported pulmonary MALT lymphoma, and fluorescence in situ hybridization detected a BIRC3::MALT1 (formerly API2-MALT1) fusion in 35% of analyzed cells. Resection margins were negative; the only separately documented LN7 lymph node showed reactive hyperplasia without lymphoma, and bone marrow examination was negative. PET/CT performed 11 days after surgery showed expected postoperative inflammatory uptake, mildly avid right upper-lobe ground-glass opacities (SUVmax 1.0), and circumferential thickening of the horizontal duodenum (SUVmax 4.0). Review of serial preoperative CT reports showed that the additional right-lung ground-glass opacities had been present since at least January 2021 and were largely stable through March 2025. Gastroscopy showed no duodenal mucosal abnormality, no biopsy was obtained, and the duodenal finding remained essentially unchanged after rituximab-based systemic therapy. The minimum confirmed extent was therefore a resected pulmonary MALT lymphoma without proven nodal, marrow, additional pulmonary, or gastrointestinal involvement.
Conclusion:
Mild FDG uptake in longstanding pulmonary opacities and an unbiopsied gastrointestinal abnormality should not be interpreted as lymphoma dissemination. Histopathology, immunophenotyping, molecular testing, longitudinal imaging, and pathologic confirmation of suspected additional sites should be integrated before disease extent and treatment response are assigned.
