NOR-1 immunostain is a good method to confirm the diagnosis of an oral acinic cell carcinoma.

Acinic cell carcinoma (ACC) is a low-grade malignant salivary gland tumor with cells that show serous acinar differentiation. Approximately 85–90% of all ACCs occur in the parotid gland. Here, we presented an exophytic polypoid tumor at the edentulous alveolar ridge of the left maxillary molar region of a 62-year-old female patient.

This 62-year-old female patient came to a private oral and maxillofacial surgery clinic for treatment of an exophytic polypoid tumor measuring 1.0 × 0.8 × 0.5 cm at the edentulous alveolar ridge of the left maxillary molar region for 2 months. Panoramic and periapical radiographies demonstrated the destruction of the superficial alveolar bone under the polypoid tumor. Although the tumor was not painful, it was partially irritated by the left mandibular molar teeth and this caused surface ulceration and bleeding from the tumor. Thus, after discussing with the patient and obtaining the signed informed consent, the polypoid tumor was excised under local anesthesia. The removed tissue specimens were sent for histopathological examination. Microscopically, the tumor was a polypoid mass with sheets of basophilic tumor cells in the subepithelial connective tissue (Fig. 1A). Medium-power and high-power views exhibited that the tumor was composed mainly of sheets of granular, basophilic serous acinic cells with some of them arranged in serous acinar structures (Fig. 1B, C, and D). Because the tumor was suspected to be an ACC, an immunohistochemical stain of the tumor tissue section for the detection of the transcription factor nuclear receptor subfamily 4 group A member 3 (NR4A3) was performed using the commercially available antibody NOR-1 (sc-393902 [H-7], Santa Cruz Biotechnology Inc., Dallas, TX, USA). Nearly all the serous acinic tumor cells showed diffuse positive nuclear staining for NR4A3 antigen by NOR-1 immunostain (Fig. 1E and F). Because nuclear expression of NR4A3 is a sensitive and specific diagnostic marker for ACC of the salivary gland, ACC was finally confirmed histopathologically.

Figure 1

Histopathological and immunostained microphotographs of the acinic cell carcinoma (ACC). (A) Low-power microphotograph showing a polypoid tumor with sheets of basophilic tumor cells in the subepithelial connective tissue. (B, C, and D) Medium-power (B) and high-power (C and D) microphotographs exhibited that the tumor was composed mainly of sheets of granular, basophilic serous acinic cells with some of them arranged in serous acinar structures (Hematoxylin and eosin stain; original magnification; A, 4×; B, 10×; C and D, 20×). (E and F) Medium-power (E) and high-power (F) immunostained microphotographs demonstrated diffuse positive nuclear staining for NR4A3 antigen in nearly all the serous acinic tumor cells (NOR-1 immunostain, original magnification; E, 10× and F, 20×).

The main purpose of this report was to emphasize that NOR-1 immunostain is a good method to confirm the diagnosis of an oral acinic cell carcinoma of the salivary gland origin. Actually, immunohistochemistry is a valuable tool that can be used to identify the tumor cell type and cell origin.2, 3, 4, 5 ACC of the salivary gland is characterized by a recurrent chromosomal arrangement (t (4; 9) (q13; q31)) that upregulates the transcription factor NR4A3. A previous study used the NOR-1 immunostain for the detection of NR4A3 in 10 low-grade ACCs of the salivary gland, one dedifferentiated high-grade ACC of the salivary gland, and 59 non-ACCs of the salivary gland. They found a distinct positive nuclear staining in all 11 ACCs but the nuclear expression of NR4A3 is absent in all non-ACCs. Therefore, they concluded that the nuclear expression of NR4A3 detected by the NOR-1 immunostain is a sensitive and specific diagnostic marker for ACCs of the salivary gland. The ACC of our case was probably arising from the acinar cells of minor salivary glands in the alveolar mucosa of the edentulous alveolar ridge of the left maxillary molar region.

Declaration of competing interest

The authors have no conflicts of interest relevant to this article.