Pulmonary lymphangitic carcinomatosis as an unusual presentation of renal cell carcinoma: a case report and a brief literature review.

Introduction: Pulmonary lymphangitic carcinomatosis (PLC) is a rare manifestation of renal cell carcinoma (RCC) that can mimic benign interstitial lung disease, creating a significant diagnostic pitfall. This case report highlights how such a misinterpretation led to inappropriate surgical management and underscores the importance of a biopsy-first approach in suspected metastatic RCC. This report follows the SCARE 2025 Checklist. Case presentation: A 53-year-old woman presented with respiratory symptoms, a left renal mass, and pulmonary interstitial changes initially misinterpreted as sarcoidosis. Based on this, she underwent a cytoreductive nephrectomy, which revealed clear cell RCC with 10% sarcomatoid differentiation. A subsequent bronchoscopy with PAX8-positive biopsy confirmed the pulmonary findings were PLC. Despite treatment with sunitinib and later pembrolizumab plus axitinib, the disease progressed rapidly, and she died 14 months after diagnosis. Clinical discussion: This case demonstrates a critical diagnostic challenge where PLC mimicked sarcoidosis. The decision to perform nephrectomy before obtaining a definitive histological diagnosis from the lungs represents a deviation from the standard of care. In cases of widespread, aggressive disease with poor-prognosis features like sarcomatoid differentiation, the benefit of upfront cytoreductive surgery is minimal, and management should prioritize systemic therapy. Conclusion: In patients, with a renal mass and suspicious pulmonary findings, a definitive histological diagnosis from the suspected metastatic site is mandatory before considering major surgery. This case strongly advocates for a biopsy-first strategy to ensure appropriate staging, guide timely systemic or palliative therapy, and avoid the morbidity of futile surgery.