NR4A3 fluorescence in situ hybridization analysis in cytologic and surgical specimens of acinic cell carcinoma

Acinic cell carcinoma (AciCC) may pose a diagnostic challenge, particularly on small biopsies and fine needle aspiration (FNA) because of its variable histology including potential high-grade transformation and its mimickers. Immunoreactivity with circumferential membranous staining for DOG1 can support the diagnosis of AciCC but is not entirely specific. A novel rearrangement t(4;9)(q13;q31) leading to up-regulation of nuclear receptor subfamily 4 group A member 3 (NR4A3) has been described in AciCC, is potentially detectable by fluorescence in situ hybridization (FISH) and may be useful in the evaluation for AciCC. Using NR4A3 Dual Color Break Apart Probe (ZytoVision, Germany) FISH was performed on AciCCs from 3 large academic institutions. NR4A3 rearrangement was defined as positive signal patterns in 15% of tissue interphase nuclei. Fifty-two AciCCs including 47 resections and 5 FNAs (including 5 paired FNA/resections) were analyzed. Five non-AciCC salivary gland tumors and 2 sialadenitis cases were used as controls. Eight AciCCs (15%; 8/52) failed FISH testing. FISH was positive in 23 AciCCs (sensitivity 59%, 23/39) with 100% concordance between 5 matched resection/FNAs (3 were positive for FISH and 2 were negative). FISH was negative in all non-AciCCs (specificity: 100%, 0/7). NR4A3 FISH has a sensitivity of 59% and specificity of 100% in detecting AciCC, which suggests that NR4A3 rearrangement-driven up-regulation is a recurrent, specific oncogenic event in AciCC, consistent with prior results. Hundred percent concordance between matched FNA/resection samples validates its potential utility on cytology samples.