A case report of unexpected rapid regression of diffuse pulmonary lymphangiomatosis mimicking advanced lung cancer.

introductionDiffuse pulmonary lymphangiomatosis (DPL) is an extremely rare lymphatic disorder characterized by diffuse proliferation of lymphatic vessels involving the lungs, pleura, and mediastinum. Its radiologic features often overlap with those of malignancy, particularly lymphangitic carcinomatosis, making accurate diagnosis challenging. CASE PRESENTATION: A 79-year-old man presented with a one-week history of dyspnea and high fever. Chest computed tomography demonstrated an enhancing pulmonary nodule with extensive mediastinal and bilateral hilar lymphadenopathy, pleural effusion, pleural thickening, and diffuse interlobular septal thickening, raising suspicion for advanced lung cancer with lymphangitic metastasis. Endobronchial ultrasound-guided transbronchial needle aspiration and pleural biopsy were nondiagnostic. Subsequently, video-assisted thoracoscopic surgery with wedge resection was performed. Histopathologic examination revealed diffuse proliferation of anastomosing lymphatic channels lined by endothelial cells, with positive immunostaining for D2-40 and CD31, consistent with DPL. Notably, without DPL-directed therapy, the patient's symptoms resolved within three weeks. Follow-up chest CT at two months demonstrated marked regression of lymphadenopathy and complete resolution of interlobular septal thickening. No clinical or radiological recurrence was observed during one year of follow-up.

conclusionDPL can closely mimic advanced lung cancer with lymphangitic metastasis on imaging while exhibiting a potentially reversible clinical course. Awareness of this entity is essential to avoid misdiagnosis and unnecessary aggressive treatment, particularly in atypical settings and for elderly patients.