Focal Positive PSMA Expression in Ganglionic Tissues Associated with Prostate Neurovascular Bundle: Implications for Novel Intraoperative PSMA Based Fluorescent Imaging Techniques.
Sheila F Faraj, Jason Solus, Joh Eifler, Turki Alhussain, Alcides Chaux, Martin Pomper, Ronald Rodriguez, George J Netto. Johns Hopkins Medical Institution, Baltimore, MD
Background: Prostate specific membrane antigen (PSMA) is a type II transmembrane glycoprotein that is primarily expressed in glandular prostate tissue. We previously demonstrated occasional PSMA expression in peripheral nerve sheath tumors. A real time intra-operative imaging technique using a newly developed low molecular weight urea-based compound that binds to PSMA and fluoresces in the NIR spectrum is being pursued at our institution. Such intra-operative techniques could help decrease the rate of positive surgical margins of radical prostatectomy (RP). In the current study we evaluated PSMA expression in neurovascular bundle elements including peripheral nerve, ganglion and lymphovascular tissue in order to assess the feasibility of the above intraoperative technology.
Design: Twenty consecutive RP specimens were retrieved from our surgical pathology archives. PSMA immunoexpression was assessed in a representative section from each specimen containing neurovascular bundle elements using a PSMA monoclonal antibody (Clone 3E6, DAKO, Denmark). PSMA expression was evaluated by two pathologists. An intensity (1 = weak, 2 = moderate, 3 = strong) and extent (1 = <25%, 2 = 25%-75%, 3 = >75%) score was assigned in each RP for available prostate carcinoma (PCa) neurovascular bundle elements and associated ganglion tissue.
Results: As expected, PSMA membranous and cytoplasmic expression was documented in 100% (11/11) of examined PCa tumors. None of the peripheral nerve and lymphovascular components of 19 examined neurovascular bundles were positive for PSMA. However, focal weak to moderate staining was detected in associated ganglionic tissue in 3/15 (20%) examined RPs.
|Tissue||PSMA Positive (%)||PSMA Intensity (n)||PSMA Extent (n)|