Pulmonary Metastases From Undiagnosed Prostate Cancer Mimicking Late Recurrence of Renal Cell Carcinoma: Diagnosis Confirmed by Thoracoscopic Biopsy.

This case report concerns a 68-year-old man who presented with enlarging pulmonary nodules 24 years after undergoing a right radical nephrectomy for renal cell carcinoma (RCC). Given the long disease-free interval and the characteristic late recurrence pattern of RCC, pulmonary metastasis of renal origin was initially suspected. Considering the potential bleeding risk associated with the hypervascular nature of metastatic RCC, video-assisted thoracoscopic surgery (VATS) was performed for a definitive diagnosis. Histopathological analysis revealed a cribriform architecture, and immunohistochemical staining was positive for prostrate-specific antigen (PSA), NKX3.1, and alpha-methylacyl-CoA racemase (AMACR), leading to a diagnosis of metastatic prostate adenocarcinoma rather than a recurrence of RCC. Subsequent evaluation identified a primary prostate cancer (Gleason score 8, cT2cN0M1), and the patient achieved a favorable response with androgen deprivation therapy. This case highlights the pitfall of "diagnostic anchoring" to a previous malignancy and emphasizes that new pulmonary lesions, even decades after an initial cancer diagnosis, necessitate histological confirmation to differentiate between recurrence and a second primary malignancy. Video-assisted thoracoscopic surgery (VATS) remains a safe and effective diagnostic approach in such clinically ambiguous scenarios.