Microscopic description:

Predominantly cystic growth pattern with papillary projections extending into the cystic spaces.

Pale staining cells with round to ovoid nuclei with minimal pleomorphism and amphophillic cytoplasm.

Focal vacuolation of the cytoplasm.

The cystic space filled with homogeneous basophilic material.

The lesion cells are positive for staining by S100 and mammaglobin.

Discussion:

Secretory carcinoma (Mammary analogue secretory carcinoma) is a low grade neoplasm of salivary glands.

Lesions are mostly seen in parotid gland (70%) but may occur anywhere including minor salivary glands.

The histologic and immunohistochemical features resemble secretory breast carcinoma. Tumors are positive for keratin 5/6, keratin 7, mammaglobin, MUC-4 and S100.

ETV6::NRTK3 gene fusion has been associated with this entity, though not pathognomonic.

Differential diagnosis includes acinic cell carcinoma, mucoepidermoid carcinoma, pleomorphic adenoma.

Overall the tumor has favorable prognosis with very few reports of recurrence of metastasis.

The following immunostains and features are useful for differentiating the different types of clear cell tumors:


References:

Damjanov I, Skenderi F, Vranic S. Mammary Analogue Secretory Carcinoma (MASC) of the salivary gland: A new tumor entity. Bosn J Basic Med Sci. 2016;16(3):237-238. doi:10.17305/bjbms.2016.1321

PMID:32910350

Bissinger O, Götz C, Kolk A, et al. Mammary analogue secretory carcinoma of salivary glands: diagnostic pitfall with distinct immunohistochemical profile and molecular features. Rare Tumors. 2017;9(3):7162. Published 2017 Oct 3. doi:10.4081/rt.2017.7162

Boliere C, Murphy J, Qaisi M, Manosca F, Fung H. Mammary Analogue Secretory Carcinoma of the Palate: Case Report and Review of the Literature. Case Rep Dent. 2019;2019:7416302. Published 2019 Feb 27. doi:10.1155/2019/7416302

Stevens TM, Kovalovsky AO, Velosa C, et al. Mammary analog secretory carcinoma, low-grade salivary duct carcinoma, and mimickers: a comparative study. Mod Pathol. 2017;30(2):312. doi:10.1038/modpathol.2016.195

CASE IMAGES