Isolated pulmonary lymphangitic carcinomatosis as the initial manifestation of renal cell carcinoma.

Pulmonary lymphangitic carcinomatosis (PLC) is a rare manifestation of metastatic disease caused by infiltration of malignant cells within pulmonary lymphatic vessels, most commonly from breast, lung, gastric, or pancreatic cancers. Lymphangitic spread from renal cell carcinoma (RCC) is exceedingly uncommon, especially when occurring without pulmonary nodules, masses, or mediastinal lymphadenopathy. We report a 68-year-old man with extensive vascular disease and a significant smoking history who presented with progressive cough and unilateral pulmonary opacities. His symptoms worsened over six weeks despite antibiotic and corticosteroid therapy. Imaging demonstrated diffuse interlobular septal and peribronchovascular thickening with recurrent pleural effusions. Initial thoracenteses revealed exudative effusions with negative cytology. Subsequent bone marrow biopsy and bronchoscopic cryobiopsy confirmed poorly differentiated carcinoma with lymphovascular invasion consistent with RCC. Positron emission tomography revealed pulmonary, pleural, and osseous metastases. Despite initiation of immune checkpoint inhibitor therapy, the patient experienced rapid respiratory decline and transitioned to comfort-focused care. This case underscores a rare presentation of RCC as isolated PLC without nodules or mediastinal lymphadenopathy. Recognition of characteristic imaging patterns and timely tissue diagnosis are essential for accurate diagnosis, prognostication, and management.