PSMA-PET/CT provided superior detection of prostate cancer lesions with better sensitivity than mpMRI. PSMA-PET/CT can be used to enhance locoregional mpMRI to provide improved detection and characterization of lesions.

The novel Gallium-68 prostate-specific membrane antigen (PSMA)-bis [2-hydroxy-5-(carboxyethyl)benzyl] ethylenediamine-diacetic acid positron emission tomography (PET) tracer is increasingly used in the evaluation of prostate cancer, particularly in the detection of recurrent disease. However, PSMA is expressed in nonprostatic tissues, as well as in other pathologic conditions. Here we illustrate such interpretive pitfalls with relevant images that one may encounter while reporting PSMA PET/CT. This study aims to show variation in physiological distribution of PSMA activity and uptake in various benign and neoplastic disorders that may be misinterpreted as prostatic metastatic disease. These pitfalls are illustrated to enhance awareness, aiding a more accurate interpretation of the study. Retrospective database of all (68)Ga PSMA PET/CT was created and reviewed. In total, 1115 PSMA PET/CT studies performed between February 27, 2015, and May 31, 2017, were reviewed. Any unusual uptake of PSMA was documented, described, and followed up. All cases were then subdivided into the following 4 categories: physiological uptake, benign pathological uptake, nonprostatic neoplastic uptake, and miscellaneous uptake. A variety of nonprostatic tissues and lesions, including accessory salivary gland, celiac ganglion, gall bladder, Paget's bone disease, reactive lymph nodes, non–small cell lung cancer, renal cell cancer, and neuroendocrine tumor, were found to show PSMA uptake. PSMA uptake is not prostate-specific and can be taken up physiologically and pathologically in nonprostatic tissue. It is important for reporting physicians to recognize these findings and instigate appropriate investigations when required while avoiding unnecessary procedures in physiological variation.

A 71-year-old man with a background of treated stage IIIB non-small cell lung cancer was referred for Ga prostate-specific membrane antigen (PSMA) PET/CT for staging of prostate cancer. In addition to the PSMA uptake in the known prostate malignancy, the study also demonstrated increased PSMA uptake in an enlarging left lower lobe lung mass with diffusely increased PSMA uptake in an enlarged thyroid gland and bilateral enlarged supraclavicular lymph nodes. Fine-needle aspiration biopsy of the thyroid gland and a left supraclavicular lymph node demonstrated metastatic adenocarcinoma from a primary lung cancer.

Ga-PSMA PET/CT is increasingly used to evaluate recurrent prostatic malignancy due to its high specificity. A 75-year-old man with a previous history of treated prostate cancer 3 years earlier presented with rising prostate-specific antigen (PSA) level and underwent Ga-PSMA PET/CT which demonstrated a PSMA-avid focus in the neck of the pancreas. Triple-phase abdominal CT demonstrated enhancement in the arterial phase and to a lesser extent the venous phase of a soft tissue mass in the neck of the pancreas. Cytological and histopathological examination of the soft tissue mass confirmed a low-grade pancreatic neuroendocrine tumor.