Unusual Case of Missed Penile Metastases on 68Ga-PSMA PET/CT

Atypical Metastases from Prostate Cancer: Alpha-Methylacyl-Coenzyme A Racemase (AMACR) as a Potential Molecular Target in Prostate-Specific Membrane Antigen-Negative Prostate Adenocarcinoma

Prostate cancer (PCa) is a high-prevalence disease usually characterized by metastatic spread to the pelvic lymph nodes and bones and the development of visceral metastases only in the late stages of disease. Positron Emission Tomography (PET) plays a key role in the detection of PCa metastases. Several PET radiotracers are used in PCa patients according to the stage and pathological features of the disease, in particular 68Ga/18F-prostate-specific membrane antigen (PSMA) ligands. Moreover, 2-deoxy-2-[18F]fluoro-D-glucose 18F-FDG PET usually shows metastases in the late stages of disease, when dedifferentiated neoplastic clones lose PSMA expression. In some cases, PCa patients may present atypical sites of metastases, with uncommon appearance at PET imaging with different radiotracers. We present the case of a patient with biochemical recurrence of PCa (ISUP Grade Group IV; PSA 4.7 ng/mL) showing atypical sites of metastases (the testis and multiple lung nodules) with absent PSMA expression and high [18F]FDG avidity. The patient showed diffuse positivity to alpha-methylacyl-coenzyme A racemase (AMACR). Moreover, a literature review was performed by collecting cases of PCa patients with atypical metastatic spread detected via PET imaging, with the aim of highlighting the relationship between atypical sites of metastases, imaging presentation, and pathology findings.

Unusual Presentation of Solitary Penile Metastasis of Prostate Cancer on 68 Ga-PSMA PET/CT

ABSTRACT

A 75-year-old patient was referred with biochemical recurrence for prostate cancer. The patient underwent 68 Ga-PSMA (prostate-specific membrane antigen) PET/CT scan, which revealed a focal PSMA activity in the proximal left lateral penile margin. Although a subsequent ultrasound did not identify the abnormality, MRI pelvis revealed a 10-mm lesion in the left proximal corpus cavernosum. This lesion was consistent with metastatic acinar adenocarcinoma of the prostate on postresection histopathology. This unusual presentation of asymptomatic, histopathology-proven, penile solitary metastases was documented 3 years after robotic-assisted laparoscopic prostatectomy and pelvic external beam radiotherapy.

Solitary Prostate Carcinoma Penile Metastasis on 18 F-DCFPyL PET/CT

ABSTRACT

An 83-year-old man was referred for an 18 F-DCFPyL PET scan for the evaluation of rising serum prostate-specific antigen level on the background of previous radical prostatectomy for prostate adenocarcinoma and urinary outflow tract obstruction requiring in-dwelling catheter insertion. The PET scan demonstrated focal increased activity (SUV max , 35.7) at the dorsal aspect of the mid penile shaft, with histopathological confirmation of penile metastasis from primary prostate cancer.

68 Ga-PSMA-11 PET/CT and 64 CuCl 2 PET/CT Help in Identifying Rare Metastatic Site of Penile Shaft in a Patient of Carcinoma Prostate

ABSTRACT

A 71-year-old man, presenting with complaints of burning sensation and pain during urination, finally diagnosed with prostate carcinoma. Ultrasonography of the abdomen and pelvis revealed prostatomegaly. Serum PSA level was elevated, and TRUS-guided biopsy demonstrated acinar adenocarcinoma (Gleason score: 5 + 4 = 9). 68 Ga-PSMA-11 PET/CT for initial staging showed PSMA-avid enlarged prostate, pelvic lymphadenopathy, and focal PSMA uptake in the left side of the shaft of the penis. The patient also underwent a 64 CuCl 2 PET/CT, which demonstrated similar findings of enlarged prostate and adenopathy with focally increased tracer uptake in the shaft of the penis coinciding with the lesion observed on 68 Ga-PSMA-11 PET/CT, thereby detecting a rare metastatic site from carcinoma prostate.