Cytogenetic and immunohistochemical characterization of Mammary Analogue Secretory Carcinoma of salivary glands

Objectives: Mammary analogue secretory carcinoma (MASC), initially considered a sub-set of acinic cell carcinoma (ACC) harbours an ETV6 translocation [t(12:15)(p13:25q)] and is now regarded as a distinct entity. Several putative markers to differentiate MASC from ACC have been reported however, the immunohistochemical profile is still being explored and updated. The purpose of this study was to further explore the cytogenetic and immunohistochemical profile of MASC. Study design: Cases were analysed for ETV6 translocation using fluorescent in situ hybridisation(FISH) and stained for CK8, amylase, mammaglobin, GCDFP 15, MUC1, MUC4, STAT5a, Ki 67 (n=37), CK7, Cam5.2, CK14, SMA, p63, S100, vimentin and DOG- 1 (n=42). Histochemical stains for mucins were also performed and data collected for age, gender and site. Results: FISH showed nine cases with ETV6 rearrangement and two with increased ETV6 copies. These eleven cases showed absence of PAS-D resistant granules with 10/11 showing strong S100, mammaglobin and Stat5a staining. All ACCs showed diffuse DOG-1 staining whereas 8/11 MASCs were negative and three showed only focal DOG1 staining. Conclusion: DOG-1 can be used in conjunction with PAS-D, S100 and mammaglobin to identify MASCs. Cases with increased ETV6 copies are a novel finding with a similar immunostaining profile and should be considered as MASCs.