Molecular analysis of a mammary analog secretory carcinoma in the upper lip: Novel search for genetic and epigenetic abnormalities in MASC

INTRODUCTION: Mammary analog secretory carcinoma (MASC) is a newly described rare malignancy of the salivary glands characterized by an ETS variant 6 (ETV6)–neurotrophic tyrosine kinase receptor type 3 (NTRK3) fusion gene (EN fusion gene). PRESENTATION OF CASE: We present a case of MASC derived from the left upper lip in a 61-year-old woman. ETV6 rearrangement was detected by fluorescence in situ hybridization (FISH). The presence of EN fusion transcripts was verified by reverse-transcriptase polymerase chain reaction (RT-PCR) and sequencing of the PCR products. Accordingly, this tumor was diagnosed as MASC. Moreover, we performed mutation analysis of the 50 known cancer-related genes using next-generation sequencing. No mutation of cancer-related genes was identified here. Subsequently, the methylation status in promoter region of tumor-suppressor genes, RASSF1A and RARB2, was examined. Both genes have been reported to be methylated in malignant salivary gland tumors, but they were found to be unmethylated. DISCUSSION: Recent studies have demonstrated that distinct types of malignant salivary gland carcinomas are driven by specific, highly recurrent genetic alterations. Detection of molecular abnormalities could be powerful diagnostic tools in the field of salivary gland tumors in near future. CONCLUSION: We experienced a rare malignant salivary gland carcinoma, MASC. We diagnosed this tumor by molecular approach and subsequently tried to identify novel molecular abnormalities. Although no novel molecular alteration except for EN fusion gene was identified, this result might represent the favorable prognosis of patients with MASC.