Expression of Prostate-Specific Membrane Antigen in Salivary Gland Tumors

Prostate-specific membrane antigen (PSMA) is a key diagnostic/prognostic, therapeutic target in prostate cancer. While PSMA expression is well established in prostate cancer, its expression is also observed in non-prostatic tissues and other tumors. PSMA expression is observed in salivary gland tumors (SGTs); however, its expression pattern is not well established. This study assessed the distribution of PSMA expression in SGT specimens.

This study retrospectively analyzed archived SGT specimens. Patient records were reviewed and their formalin-embedded tumor blocks were retrieved from the pathology department files. Immunohistochemical staining and examination was performed using an antibody directed against PSMA to assess expression levels in 243 salivary gland specimens containing 126 specimens of malignant and 117 specimens of benign SGTs. PSMA staining was quantified using a modified immunohistochemical scoring method (H score; range 0-300).

PSMA expression was observed in both benign SGTs and malignant SGTs; however, PSMA expression in malignant SGTs was higher than in benign SGTs. PSMA was expressed in 94% (118/126) of malignant SGTs (represented as average histochemical [H_avg] score, [Havg = 95.2]), and 61% (71/117) of benign SGTs (H_avg = 37.3). Amongst malignant SGT specimens, the highest H_avg scores were observed for adenoid cystic carcinoma (H_avg = 133.7) and acinic cell carcinoma (H_avg = 133.6). Based on the modal staining intensity scoring, strong PSMA staining (staining intensity score = 3) was observed at higher rates in malignant (38%, 48/126) versus benign (18%, 21/117) SGTs.

This study demonstrated that PSMA is commonly expressed in malignant SGTs, suggesting that PSMA could be effective for targeted imaging and therapeutics in these tumor types.