Prostate carcinoma metastasizing to a chromophobe RCC: how o
The existence of synchronic tumors is a relatively frequent phenomenon. On the other hand, a tumor metastasis from a distant site to a second primary tumor is a rare event. The metastasis between two true primary tumors is known as a tumor-to-tumor metastasis.

This unusual phenomenon has been described in a small number of cases and clear cell RCC appears to be the main tumor receptor of these metastases. Published in Urology Case Reports, the authors present an extremely rare case of prostate adenocarcinoma metastasizing to a chromophobe RCC.

An 80-year-old man with a metastatic prostate cancer, at the initial prostate biopsy had an adenocarcinoma group 2 (Gleason score 7 (3 + 4)) and a prostate specific antigen (PSA) of 917 ng/mL. At diagnostic evaluation, extensive bone metastasis were identified on the bone scan. During follow up, the patient presented with acute urinary retention requiring a transurethral resection of the prostate with a bilateral orchiectomy as a definitive androgen deprivation therapy, improving voiding pattern, and decreasing the total PSA to 70.7 ng/mL.

After 10 months of surgical castration, PSA continued to rise so a complete androgen blockade was attempted with bicalutamide, and a PSA nadir of 26.2 ng/mL was achieved. The testosterone level was <20 ng/dL. Twelve months latter a computerized tomography was performed and a right-sided 4.6 cm solid renal lesion with close proximity to the renal sinus was identified.

The patient underwent and uneventful laparoscopic right partial nephrectomy, microscopic analysis revealed a chromophobe type RCC, the tumor was limited to the kidney and the resection margins were negative, it was staged as pT1b according to the 2010 TNM classification system.

In addition, a focal prostatic adenocarcinoma with cribriform pattern infiltrating the renal neoplasm was identified. This was confirmed by immunohistochemistry analysis with positivity for PSA, PSAP, Racemase and androgen receptor markers, therefore the final diagnosis was a tumor-to-tumor metastasis from prostate adenocarcinoma to chromophobe RCC.

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