Abstract Introduction Pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma is a rare extranodal marginal zone B-cell lymphoma, accounting for less than 1% of all primary pulmonary malignancies. A nonspecific presentation and uncertain radiographic demonstration makes for a challenging diagnosis, often mimicking an infectious or inflammatory lung pathology. Gold standard diagnosis includes histopathologic confirmation, however biopsies frequently prove nondiagnostic secondary to the disease state’s submucosal nature and variable presentations. Prolonged diagnostic courses are a burdensome road to traverse, often including surgical biopsies and other invasive interventions. Case Report A 42-year-old woman with a 25-pack year smoking history and DVT presented to her primary care provider with mild dyspnea and left chest pressure. Noted to have a positive d-dimer prompting a CT scan that was negative for pulmonary emboli, but noted multiple, bilateral pulmonary nodules, the largest of which being 1 cm prompting pulmonary referral. She denied hoarseness, loss of appetite, weight loss, hemoptysis, pain, fever, chills, or night sweats. She denied exposure to asbestos, TB, or positive PPD. No family history of lung cancer. PET scan showed focal uptake in the right medial lobe nodule as well as the uterus and anus. Pelvic US demonstrated no urogenital abnormality and repeat CT abdomen showed stable inguinal and pelvic adenopathy and a stable enlarged portacaval lymph node. Extensive autoimmune and infectious workup proved negative. Despite this, treated repeatedly for both viral and bacterial pneumonias, obstructive sleep apnea, and anxiety. Repeat CT scans with slowly progressing nodule growth. Underwent robotic navigational bronchoscopy to sample the right lower lobe nodule, and results were deemed reactive. Transbronchial biopsies showed dense lymphoplasmacytic infiltrate favoring reactive disease. She also had an endobronchial ultrasound guided biopsy showing reactive lymphocytes without evidence of malignancy or granulomas. Cultures were all negative. Repeat robotic navigational bronchoscopy showing again lymphoplasmacytic and histiocytic inflammatory infiltrate with negative flow. Ultimately, she then underwent surgical lung biopsy showing MALT lymphoma with marked plasmacytic differentiation. She was initiated on Rituxin monotherapy, and continues on treatment. Discussion This interesting case highlights the elusive diagnostic difficulty of pulmonary MALT lymphoma. Nonspecific imaging findings, such as seen in this case report, inconclusive bronchoscopy findings, and the subclinical progression of disease results in significant diagnostic delays. Providers should maintain a high degree of suspicion in patients with persistent, unexplained lung infiltrates that fail to respond to typical therapies. Prompt diagnosis enables the initiation of targeted therapy and prevents unnecessary workup and treatment. This abstract is funded by: none
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