Diagnosis of acinic cell carcinoma of the salivary gland on cytology specimens: Role of NOR-1 (NR4A3) immunohistochemistry.

OBJECTIVES: Acinic cell carcinoma (AcCC) is often a challenging diagnosis on cytology. Recently, NOR-1 (NR4A3) has been demonstrated as a sensitive and specific marker for AcCC. Therefore, we conducted this study to evaluate NOR-1 expression in AcCC cytology specimens and to compare its reactivity in other salivary gland tumours (non-AcCC). METHODS: We retrospectively reviewed our database and selected cytology cases with available cell blocks, including 10 AcCC and 24 non-AcCC tumours (12 benign tumours and 12 malignant tumours). NOR-1 (1:50 dilution; SC393902 [H-7]; Santa Cruz Biotech) immunohistochemistry (IHC) was performed on all cases. RESULTS: All AcCC cases except two (2/10, 80%) showed positive nuclear staining of variable intensity for NOR-1, with the majority of cases (75%) demonstrating at least moderately intense nuclear expression. All non-AcCC cases were negative for NOR-1, demonstrating a specificity of 100%. CONCLUSION: We conclude that NOR-1 IHC is sensitive and very specific on cytology specimens and is able to distinguish AcCC from its mimickers reliably and classify them appropriately for further management.