Impact of PSMA PET/CT in prostate cancer patient’s clinical management: a pictorial essay of interesting cases with histologic confirmation

Introduction: Prostate-Specific Membrane Antigen (PSMA) Positron Emission Tomography (PET) has a significant impact on prostate cancer (PCa) patient’s clinical management. PSMA PET/CT has changed both the paradigm of metastases spread pathway, and the PSMA specificity for detecting PCa lesions. Currently, it is accepted that PCa can spread to cervical and mediastinal lymph nodes without other intermediate lesions. PSMA expression in non-prostate cancers or benign lesions is known as well. However, information about PSMA functional specificity in clinical practice is still missing. Methods: A retrospective analysis of PSMA PET/CT studies was done to select relevant clinical cases with complete clinical history, histology results and follow-up information. Each clinical case was organized from a holistic perspective, including clinical information, ⁶⁸Ga-PSMA PET/CT images, pathology results and clinical outcome. Results: Nine clinical cases were selected to illustrate synchronous primary cancers (gastric gastrointestinal stromal tumours and clear cell renal cell carcinoma), atypical sites of PCa metastases (thyroid, liver, cervical and mediastinal lymph nodes) and some examples of PCa lung metastases with discordant PSMA findings between PET/CT examinations and immunohistochemistry. Discussion: In this pictorial essay and review, the meaning of high PSMA expression in neovasculature and uncommon PCa metastatic spread were addressed. Furthermore, recent information about the possible explanation of (1) PCa metastases without PSMA expression due to dedifferentiation and specific PCa subtypes, and (2) some discordant findings on PSMA expression evaluated by PET/CT and immunohistochemistry related to the anti-PSMA antibody used in each technique is presented.