Mammary analogue secretory carcinoma (MASC) is a new conception of the salivary gland tumor proposed by Skalova et al. in 2010. It was described as “secretory carcinoma” in the 2017 edition of the WHO classification of Tumors. In this report, we describe a case of secretory carcinoma (SC) in a 51-year-old woman. She was referred to our hospital because of a painless, movable mass in the lower lip. The lesion was a soft, elastic mass, 10 × 15 mm in size, found within the mucosa of the lower right lip with no vasodilation.
Based on ultrasonography and MRI results, the tumor was suspected to be a benign salivary gland tumor, so we planned a resection biopsy. Histopathological examination revealed a variety of images, including follicular structures resembling thyroid follicles, papillary growth of tumor cells, eosinophilic secretions, and cholesterol clefts. As we suspected a malignant tumor, immunostaining was performed. The results were CK19 (+), S-100 protein (+), p63 (−), and mammaglobin (+). Based on these findings, SC was strongly suspected, so a gene search was performed. As a result, the ETV6-NTRK3 fusion gene was detected, leading to a definitive diagnosis of SC.
In the two years after the operation until now, the patient has been free of recurrence or metastasis and is without disease.
