Cytogenetic and immunohistochemical characterization of mammary analogue secretory carcinoma of salivary glands.

OBJECTIVES Mammary analogue secretory carcinoma (MASC), initially considered a subset of acinic cell carcinoma (ACC), harbors an ETV6 translocation [t(12:15)(p13:25 q)] 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 analyzed for ETV6 translocation using fluorescent in situ hybridization and stained for CK8, amylase, mammaglobin, GCDFP-15, MUC1, MUC4, STAT5a, Ki-67 (n = 37), CK7, Cam5.2, CK14, SMA, p63, S100, vimentin and DOG1 (n = 42). Histochemical stains for mucins were also performed and data collected for age, sex, and site. RESULTS Fluorescent in situ hybridization showed 9 cases with ETV6 rearrangement and 2 with increased ETV6 copies. These 11 cases showed an absence of PAS-D-resistant granules, with 10 of 11 showing strong S100, mammaglobin, and STAT5a staining. All ACCs showed diffuse DOG1 staining, whereas 8/11 MASCs were negative and 3 showed only focal DOG1 staining. CONCLUSION DOG1 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.