Mammary Analogue Secretory Carcinoma of Salivary Gland Origin: An Update and Expanded Morphologic and Immunohistochemical Spectrum of Recently Described Entity

Abstract

Mammary analogue secretory carcinoma of salivary gland origin (MASC) is a recently described tumor with ETV6 translocation. Akin to secretory breast cancer, MASC expresses S-100 protein, mammaglobin, vimentin, and harbors a t(12;15) (p13;q25) translocation which leads to ETV6-NTRK3 fusion product. Histologically, MASC displays a lobulated growth pattern and is often composed of microcystic, tubular, and solid structures with abundant eosinophilic homogeneous or bubbly secretions. Colloidlike secretory material stains positive for periodic acidSchiff (PAS) with and without diastase and for Alcian blue. The cells of MASC are devoid of PAS-positive secretory zymogen granules. These features help to exclude the most important differential diagnostic considerations, namely acinic cell carcinoma, low-grade cribriform cystadenocarcinoma, cystadenocarcinoma (not otherwise specified), and low-grade mucoepidermoid carcinoma. To date the presence of the ETV6-NTRK3 fusion gene has not been demonstrated in any other salivary gland tumor than MASC. It is likely that MASC is more common than currently recognized and with further studies, the clinical need for molecular studies of the ETV6-NTRK3 fusion may diminish. However, molecular testing is recommended at this time to arrive at the diagnosis of MASC.

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

“…S100 staining was seen in 11/31 ACCs but appeared much weaker and restricted compared to MASCs. This is in agreement with previous reports showing that diffuse and strong S100 expression may distinguish MASCs from ACCs [1,7]. Mammaglobin and S100 have also been suggested as proxy markers for MASC [22].…”

“…However, this study investigated nineteen cases of MASC, but included only one ACC making the staining specificity somewhat uncertain. One suggested criterion is that S100 expression must be strong and diffuse [7], but others have shown that S100 can be variably expressed in ACC and other tumours may show strong diffuse expression [8]. The correct diagnosis may have implications with respect to clinical behaviour and the presence of a specific chromosomal translocation offers a potential target for future biological therapy.…”

A Case of Primary Mammary Analog Secretory Carcinoma (MASC) of the Thyroid Masquerading as Papillary Thyroid Carcinoma: Potentially More than a One Off

“…Notably, multiple authors have described some patterns found in MASC as appearing similar to thyroid colloid-like deposition or a follicular pattern of thyroid carcinoma [1,3,7,17]. Nuclear features of our patient's tumor also resembled closely those of PTC in that the nuclei were vesicular with numerous nuclear grooves.…”

Mammary analog secretory carcinoma, low-grade salivary duct carcinoma, and mimickers: a comparative study

“…1 The recurrent t(12;15) (p13;q25) rearrangement results in the fusion of ETV6, a transcriptional regulator on 12p13, with NTRK3, which encodes a membrane tyrosine kinase receptor. 12,13 This same ETV6/NTRK3 fusion is also characteristic of secretory carcinoma of the breast, a tumor that is histologically identical to MASC, as well as congenital mesoblastic nephroma, congenital fibrosarcoma, and some forms of acute myeloid leukemia. 6 Subsequent reports of MASC broadened the histologic range of this neoplasm, as macrocystic, polypoid, and papillocystic patterns and perineural invasion were described.…”