NOR-1 (NR4A3) immunostaining on cytologic preparations for the preoperative diagnosis of acinic cell carcinoma of the salivary gland.

Introduction: Acinic cell carcinoma of the salivary gland (ACC-SG) is characterized by recurrent rearrangements in the nuclear receptor subfamily 4 group A member 3 (NR4A3). Immunostaining using an antibody targeting this rearrangement, neuron-derived orphan receptor 1 (NOR-1), has been recently studied on surgical specimens and cell block material of fine-needle aspirates for the diagnosis of ACC-SG. Our goal was to evaluate whether NOR-1 immunostaining could reliably be performed on destained cytologic preparations.
Materials and Methods: This was a retrospective multi-institutional study. Immunostaining with the NOR-1 antibody (sc-393902 [H-7], Santa Cruz Biotechnology Inc.) was performed at a titer of 1:30 on destained cytologic preparations. ACC-SG cases (n = 17) were represented by twelve cases with alcohol-fixed preparations (n = 12), including direct smears and SurePath preparations, as well as 5 cases with air-dried preparations (n = 5). These were compared to 27 mimicker lesions (n = 27): normal acini (4), chronic sialadenitis (3), oncocytoma (2), pleomorphic adenoma (6), Warthin tumor (8), mucoepidermoid carcinoma (1), secretory carcinoma (2), and salivary duct carcinoma (1).
Results: The positivity of NOR-1 in ACC-SG cases was 100% on destained alcohol-fixed preparations (12/12) and 60% on air-dried preparations (3/5). All 27 mimicker lesions were negative for NOR-1 (0/27). Evaluation of 2 ACC-SG cases with both types of cytologic preparations showed that NOR-1 was positive on the alcohol-fixed slides but negative on the air-dried slides.
Conclusions: NOR-1 immunostaining can reliably be performed on alcohol-fixed direct smears and liquid-based preparations for the diagnosis of ACC-SG. Air-dried preparations show a lower positivity rate and may be less suitable for diagnostic immunostaining.
(Copyright © 2022 American Society of Cytopathology. Published by Elsevier Inc. All rights reserved.)