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.