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

## TL;DR

A man with a history of kidney cancer was found to have prostate cancer metastases in his lungs, showing the importance of accurate diagnosis.

## Contribution

Highlights the diagnostic challenge of distinguishing between cancer recurrence and new malignancies using VATS and immunohistochemistry.

## Key findings

- Pulmonary nodules initially thought to be RCC recurrence were diagnosed as metastatic prostate cancer via VATS.
- Histopathology and immunohistochemical staining confirmed prostate adenocarcinoma with Gleason score 8.
- The patient responded well to androgen deprivation therapy after correct diagnosis.

## Abstract

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.