Persistent multifocal pulmonary consolidations in a young adult: An unusual presentation of primary pulmonary follicular lymphoma.

Primary pulmonary lymphoma (PPL) is rare malignancies, accounting for less than 1% of primary lung malignancies and extranodal lymphomas. Primary pulmonary follicular lymphoma is an uncommon subtype of PPL. Herein, we report the case of a 29-year-old immunocompitent man who presented with persistent pulmonary infiltrations despite appropriate antibiotic treatment for presumed pneumonia. Computed tomography (CT) of chest revealed multifocal consolidations with surrounding ground-glass opacities, predominantly involving the peripheral and lower lung zones, along with multiple mediastinal lymphadenopathy. Brochoscopy with bronchoalveolar lavage cultures and microbiological investigation, including tests for bacterial, mycobacterial, and fungal pathogens, were all negative. Histological examination of transbronchial biopsy (TBBx) demonstrated atypical B-cell lymphoproliferation, Immunohistochemistry was positive for CD20, CD10, BCL2, and BCL6, while AE1/AE3 and thyroid transcription factor-1 (TTF1) highlighted reactive pneumocytes. No evidence of any extrathoracic manifestration is comfirmimg the diagnosis of primary pulmonary follicular lymphoma. The patient was treated with rituximab, cyclophosphamide, vincristine, and prednisolone (R-CVP), resulting in significant clinical and radiographic improvement. This case highlights the diagnostic challenge of primary pulmonary follicular lymphoma, which may mimic chronic pulmonary infection, particularly in young immunocompetent patients. Persistent pulmonary consolidations despite appropriate antimicrobial therapy should prompt consideration of early tissue diagnosis to exclude an underlying malignancy.