Metastasis in urothelial carcinoma mimicking prostate cancer metastasis in Ga-68 prostate-specific membrane antigen positron emission tomography-computed tomography in a case of synchronous malignancy

Prostate cancer is the second most common cancer in man. It commonly presents with urinary symptoms, bone pain, or diagnosed with elevated prostate-specific antigen (PSA) levels. Correct staging and early diagnosis of recurrence by a precise imaging tool are the keys for optimum management. Molecular imaging of prostate cancer with Ga-68 prostate-specific membrane antigen (PSMA), positron emission tomography-computed tomography (PET-CT) has recently received significant attention and frequently used with a signature to prostate cancer-specific remark. However, this case will highlight the more cautious use of it. A 72-year-old male treated earlier for synchronous double malignancy (invasive papillary urothelial carcinoma right ureter and carcinoma prostate) presented with rising PSA (0.51 ng/ml) and referred for Ga-68 PSMA PET-CT, which showed a positive enlarged left supraclavicular lymph node. Lymph node biopsy microscopic and immunohistochemistry examination revealed metastatic carcinoma favoring urothelial origin. Specificity of PSMA scan to prostate cancer has been seen to be compromised in a certain situation mostly due to neoangiogenesis, and false positives emerged in renal cell cancer, differentiated thyroid cancer, glioblastoma, breast cancer brain metastasis, and paravertebral schwannomas. Understanding the causes of false positive will further enhance the confidence of interpretating PSMA scans.