Prostate-Specific Membrane Antigen PET/CT: False-Positive Results due to Sarcoidosis?

Area of Science:

• Nuclear Medicine
• Oncology
• Pathology

Background:

• A 72-year-old male with a history of sarcoidosis developed prostate carcinoma.
• Initial treatment included transurethral resection, radical prostatectomy, and antihormonal therapy for advanced prostate cancer.
• Following treatment, elevated prostate-specific antigen (PSA) levels raised suspicion of recurrence.

Observation:

• A ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET/CT scan indicated local recurrence, pelvic lymph node metastasis, and hepatic metastasis.
• Ultrasound with contrast medium could not confirm liver metastasis.
• Radiotherapy was administered for the suspected recurrence, resulting in significant shrinkage.

Findings:

• The patient remained disease-free for two years post-radiotherapy, questioning the initial PSMA-PET/CT findings.
• The observed shrinkage of the 'recurrence' after radiotherapy suggests a non-malignant etiology.
• The authors hypothesize that sarcoidosis recurrence may have caused false-positive PSMA-PET/CT results.

Implications:

• This case highlights the potential for sarcoidosis to interfere with PSMA-PET/CT imaging interpretation in prostate cancer patients.
• Clinicians should consider sarcoidosis as a differential diagnosis for unexpected findings on PSMA-PET/CT, especially in patients with a history of the condition.
• Further research is warranted to elucidate the mechanisms behind PSMA uptake in sarcoidosis and its impact on diagnostic accuracy.