Abstract
Secretory carcinoma （SC） is a type of salivary gland malignant tumor and has been reported to be a mammary analogue secretory carcinoma due to its morphological resemblance to secretory carcinoma of the breast. SC is newly listed in the WHO Classification of Head and Neck Tumors （4th edition） as a slow-growing and low-grade malignant tumor of the salivary gland. SC may have been diagnosed as acinic cell carcinoma or adenocarcinoma not otherwise specified. Herein, we present four cases of SC regarding histopathological and immunochemical findings and an expression of specific ETV6-NTRK3 fusion genes. Of the four cases, the submandibular and parotid glands were involved in one and three cases, respectively. All patients were male, and the age ranged from 46 years to 63 years. There were no cases of facial palsy before treatment and no specific findings on the sonogram or magnetic resonance imaging scan. SC was suspected in Case 1 from preoperative fine-needle aspiration cytology with immunochemical staining by Pan-Trk and NOR-1. Malignancy was suspected in Case 4 although the histological type was inconclusive. Surgery was performed in all cases. In two patients （Cases 1 and 4）, postoperative radiation was performed due to the close surgical margin. The diagnosis of SC was made based on histopathological findings, immunochemical staining （mammaglobin, S-100, Pan-Trk, and NOR-1）, and the presence of ETV6-NTRK3 fusion genes. In three cases （Cases 2, 3, and 4）, the ETV6-NTRK fusion gene was detected by the RT-PCR or FISH method. In Case 1, detection of fusion gene was not performed because of the immunochemical positivity of Pan-Trk which has a high specificity for NTRK3 fusion, and negativity of NOR-1 for acinic cell carcinoma. The post-treatment course was uneventful, and Case 4 was well without recurrence or metastasis for 5 years.
