Diagnostic Challenges and Management Strategies of Pulmonary Mucosa-associated Lymphoid Tissue Lymphoma: A Case Report and Literature Review

Yang Bai^1*Bijun Yang¹Jian Tang²

• ¹First Affiliated Hospital of Chongqing Medical University, Chongqing, China
• ²The People's Hospital of Neijiang Dongxing District, Neijiang, China

Background: Pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma is a rare extranodal B-cell lymphoma, representing the most common primary pulmonary lymphoma (< 0.5% of all lung malignancies). Diagnosis is difficult because of its nonspecific clinical and radiological characteristics, which often resemble infections, inflammatory diseases, or other malignancies. Typical imaging findings include nodules, consolidations, or, less frequently, interstitial patterns such as ground-glass opacities. A conclusive diagnosis requires histological examination, augmented by immunohistochemistry and molecular investigations, to confirm clonality. Conventional biopsies may yield inconclusive outcomes due to small sample size and delicate cytologic atypia. Case Presentation: A 36-year-old non-smoking Asian female with no history of pulmonary tuberculosis, malignancies, or autoimmune disorders was incidentally found to have patchy opacities in the left lower lobe on routine chest radiography in January 2024. She remained asymptomatic over the 18-month disease progression period, lacking respiratory or systemic symptoms, whereas follow-up imaging indicated progression to bilateral, multifocal flocculent opacities. Initial investigations, including transbronchial forceps biopsy and bronchoalveolar lavage fluid analysis through next-generation sequencing, reported only non-specific chronic inflammation and no pathogens. Empirical treatment with moxifloxacin (400 mg daily for 14 days), targeting common pathogens of community-acquired pneumonia, yielded no improvement. A definitive diagnosis was achieved by endobronchial ultrasound-guided transbronchial cryobiopsy (EBUS-TBCB), which produced larger, well-preserved tissue specimens. Histopathological and immunohistochemical examination indicated a dense, angiocentric infiltration of CD20-positive B cells, accompanied by monoclonal rearrangement of immunoglobulin genes, confirming extranodal marginal zone lymphoma of the MALT type. Staging with 68Ga-CXCR4 positron emission tomography (PET)/computed tomography (CT) demonstrated hypermetabolism in bilateral pulmonary opacities and multiple nodal stations, indicative of Stage IV disease. Considering the asymptomatic status and excellent performance status, active surveillance was recommended in this patient. Conclusion: This case illustrates the important role of advanced biopsy techniques, such as EBUS-TBCB, in acquiring sufficient tissue for diagnosing pulmonary MALT lymphoma when conventional methods fail. It further underscores the 68Ga-CXCR4-targeted PET/CT for precise staging. Despite the advanced stage, the indolent nature of MALT lymphoma often allows for a plan of active surveillance in selected asymptomatic patients, emphasizing the crucial role of a multidisciplinary, risk-adapted strategy.