Between a rock and a hard place: Papillary renal cell carcinoma with synchronous lung adenocarcinoma

• Author Details:   
• Arpit Jain ^*
• Varun Goyal
• Akanksha Jaju
• Nivedita Patnaik
• Vacchani Krunal Karsanbhai
• Vineet Talwar

The simultaneous occurrence of two carcinoma is unusual and pose significant diagnostic and therapeutic challenges in differentiating a secondary lung malignancy from metastatic RCC. A 55-year-old male was diagnosed with Type 1 papillary RCC and underwent nephron-sparing surgery for a localized left renal tumor. On postoperative surveillance, a solitary right upper lobe lung nodule was detected. Histopathological evaluation of the lung lesion initially suggested metastatic RCC; however, immunohistochemistry (IHC) confirmed a separate primary lung adenocarcinoma (thyroid transcription factor-1 (TTF-1) positive, PAX8 negative) harboring EGFR mutations. The patient’s RCC was organ-confined (pT1a) and managed surgically, while the lung adenocarcinoma was treated with targeted EGFR tyrosine kinase inhibitor therapy (Osimertinib). Radiologically and clinically, metastatic RCC can mimic a new primary lung cancer and vice versa, necessitating tissue diagnosis for accurate classification. IHC and molecular profiling were pivotal in distinguishing the two malignancies, directly influencing treatment choices. The RCC’s favorable features (papillary Type 1, low grade, negative margins) portended an excellent prognosis with surgery alone, whereas identification of an actionable mutation in the lung adenocarcinoma enabled personalized systemic therapy. We discuss the rarity of synchronous RCC and lung cancer, the need for vigilance in such presentations, and provide a comparative overview of features differentiating metastatic RCC from primary lung adenocarcinoma.