Burned-out Prostate Cancer ? Primary Metastatic Cancer Not Detected on Repeat Biopsy.

Metastatic prostate cancer (PCa) cases that cannot be detected on repeat prostate biopsy are extremely rare. Our patient was a 51-year-old Japanese man diagnosed as metastatic PCa by histopathological examination of lesions obtained bone biopsy and lymph node dissection. The primary tumor was not detected after repeated prostate biopsy. Metastatic PCa was diagnosed based on immunohistochemical staining: PSA, AR, P504S, and NKX3.1 of bone and lymph node with metastasis. We speculate that the primary PCa was "burned-out," demonstrating remote metastases with no apparent primary tumor in the prostate. Burned-out PCa may be difficult to diagnose and treat due to its rarity.