2346

FOLH1

folate hydrolase (prostate-specific membrane antigen) 1;FOLH1;folate hydrolase (prostate-specific membrane antigen) 1

N-acetylated alpha-linked acidic dipeptidase 1|N-acetylated-alpha-linked acidic dipeptidase I|NAALADase I|cell growth-inhibiting gene 27 protein|folylpoly-gamma-glutamate carboxypeptidase|glutamate carboxylase II|glutamate carboxypeptidase 2|glutamate car

11p11.2

protein-coding

Prostate-specific membrane antigen (PSMA) has been found to be expressed in the tumor-associated neovasculature of multiple solid tumor types including breast cancers. However, thus far, the number of cases studied from some tumor types has been limited. In this study, we set out to assess PSMA expression in the tumor-associated vasculature associated with invasive breast carcinomas in a sizable cohort of patients. One hundred and six patients with AJCC stage 0-IV breast cancer were identified. Ninety-two of these patients had primary breast cancer [invasive breast carcinoma with or without co-existing ductal carcinoma in situ (DCIS) (74) or DCIS alone (18)]. In addition, 14 patients with breast cancer metastases to the brain were identified. Immunohistochemical staining for PSMA and CD31 was performed on parallel representative tumor sections in each case. tumor-associated vascular endothelial cell PSMA immunoreactivity was semi-quantitatively assessed based on two parameters: overall percent of endothelial positivity and staining intensity. PSMA expression for tumor-associated vascular endothelial cells was scored 0 if there was no detectable PSMA expression, 1 if PSMA staining was detectable in 5-50%, and 2 if PSMA expression was positive in >50% of microvessels. CD 31 staining was concurrently reviewed to confirm the presence of vasculature in each case. tumor-associated vasculature was PSMA-positive in 68/92 (74%) of primary breast cancers and in 14/14 (100%) of breast cancers metastatic to brain. PSMA was not detected in normal breast tissue or carcinoma cells. All but 2 cases (98%) showed absence of PSMA expression in normal breast tissue-associated vasculature. The 10-year overall survival was 88.7% (95%

OBJECTIVES: Radioimmunoscintigraphy using a radiolabeled antibody against prostate-specific membrane antigen (PSMA) is frequently used to detect prostate carcinoma (PCa) recurrence and metastasis to lymph nodes, soft tissues, and bone. PSMA expression has been shown in occasional nonprostatic neoplasms (e.g., urothelial adenocarcinoma) and in the vasculatures of other malignancies. PSMA expression has not been described in benign neoplasms. Recently, during evaluation of a prostatic carcinoma patient, we encountered a false positive PSMA radioimmunoscintigraphy scan in a pathologically confirmed Schwannoma (SCH) lesion. The current study further evaluates PSMA expression in Schwannomas. METHODS: Eleven SCH were retrieved from our surgical pathology archives. Representative sections were immunostained with monoclonal antibody for PSMA. PSMA expression was evaluated in tumor cells and lesional vessels. Extent of staining was calculated as percent of positive cells in highest areas of expression. Positive staining was considered focal, multifocal, or diffuse based on the percent of positive cells: <5%, 5% to 75%, and >75%, respectively. RESULTS: All 11 SCH showed tumoral and or vascular staining; 7 (7/11) displayed both vascular and tumoral cell staining; the remaining 4 had only vascular staining (2/11) or tumor cell staining (2/11). The extent of tumoral cell and vascular staining varied widely among lesions (tumor cells: focal in 8 and diffuse in 1; vascular: focal in 7, multifocal in 1, and diffuse in 1 lesion). CONCLUSION: This is the first report of PSMA expression in a benign neoplasm. Given our finding of frequent expression of PSMA in Schwannomas, they should be clinically considered in the differential diagnosis of a lesion that is positive on PSMA radioimmunoscintigraphy study performed during a metastatic work-up of PCa patient.