Testicular Incidentaloma on ¹⁸F-choline PET/CT in a Patient with Prostatic Adenocarcinoma

Prostatic adenocarcinoma is characterized by elevated phosphatidylcholine metabolism. ¹⁸F-choline positron emission tomography/computed tomography (PET/CT) is widely used for patients with biochemical recurrence and a prostate-specific antigen threshold above 2 ng/mL. We report a case of a patient with high-risk prostatic adenocarcinoma undergoing ¹⁸F-choline PET/CT for biochemical recurrence. In addition to hypermetabolic abdominal lymph nodes, an unexpected right testicular hypermetabolism was observed. Such findings on ¹⁸F-choline PET/CT may suggest a primary tumor or testicular metastasis of prostate cancer. Bilateral orchiectomy revealed a vitelline tumor associated with known primary prostatic cancer. The incidental discovery of a testicular vitelline tumor during prostate cancer imaging is rare, highlighting the importance of thorough diagnostics. This case underscores the need for comprehensive care in managing complex and atypical cancer cases, emphasizing the potential for unrelated tumor discoveries during diagnostic workup. Further research is essential for a better understanding of these rare co-occurring cancers and their treatment implications.