Diagnosing pulmonary MALT lymphoma: a case of unilateral cystic lesions

We present an atypical case of a 62-year-old female diagnosed with pulmonary mucosa-associated lymphoid tissue (p-MALT) lymphoma, which uniquely manifested as a singular cystic lesion in the lung. Diagnostic evaluations, including comprehensive imaging, bronchoscopy, and CT-guided lung biopsy, revealed this uncommon radiological presentation. Detailed histopathological and immunohistochemical assessments further supported the diagnosis. To determine the extent of the disease, systemic evaluations, such as whole-body PET–CT, gastroscopy, colonoscopy, and bone marrow biopsy, were conducted, confirming its localized nature. Following the definitive diagnosis, the patient underwent a rituximab-centric therapeutic regimen, which yielded significant clinical improvement. This case highlights the importance of recognizing distinctive cystic lung features in p-MALT lymphoma and the indispensable role of holistic diagnostic approaches in guiding precise therapeutic and prognostic decisions. A rare type of lung lymphoma, called p-MALT lymphoma, was found in a patient as a single, thick-walled cyst in the lung. This is unusual because these lymphomas typically look like lumps or swollen lymph nodes in the chest on scans. To figure out what was going on, doctors did several tests, including a special biopsy guided by a CT scan, a camera scope in the airways, and full-body imaging. All these tests showed the lymphoma was only in one spot and hadn’t spread. Lab tests and tissue analysis helped confirm it was lymphoma and not something harmless like an infection or a benign cyst. The patient was treated with a targeted drug called rituximab, which worked well and improved their symptoms. This case shows two important things: first, doctors should consider p-MALT lymphoma when they see unusual single cysts in the lung, especially if the cyst walls are irregular or the lung tissue looks pulled in. Second, it highlights the need for teams of specialists—like radiologists, pathologists, and oncologists—to work together to diagnose and treat rare conditions effectively. By sharing this story, we hope to help other patients with similar symptoms get the right diagnosis and care faster. p-MALT lymphoma manifested as a solitary, thick-walled cystic lung lesion, deviating from typical radiological patterns (e.g., nodular or hilar lymphadenopathy). Comprehensive evaluation—including CT-guided biopsy, bronchoscopy, and systemic workup (PET–CT, endoscopy, bone marrow biopsy)—confirmed localized disease. Immunoassays and histopathology distinguished lymphoma from benign cystic entities (e.g., bullae, infections) and mimics like cystic carcinoma. Rituximab-based therapy achieved significant clinical improvement, underscoring efficacy in localized p-MALT lymphoma. Highlights the need to include p-MALT lymphoma in differential diagnoses for solitary pulmonary cysts with atypical features (e.g., irregular walls, pleural contraction). Emphasizes collaboration between radiology, pathology, and oncology to optimize diagnostic and therapeutic strategies in rare presentations.