Strong PSMA Radioligand Uptake by Rectal Carcinoma: Who Put the "S" in PSMA?

We present a case of a 71-year-old patient with newly diagnosed rectal adenocarcinoma and hepatic metastases. Restaging after chemotherapy revealed a good response of the rectal primary while liver metastases were progressive. As the patient also had a history of prostate cancer, a Ga-PSMA-HBED-CC PET/CT scan was performed to noninvasively further assess hepatic metastases. However, a definite differentiation between tumor entities was not possible because not only the liver metastases but also the rectal primary showed radioligand uptake (moderate and strong, respectively). Consecutive liver biopsy revealed a poorly differentiated adenocarcinoma of intestinal origin.