23 March 2016 - Case of the Week #382

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Case of the Week #382

Clinical history:
A 39 year old woman presented with a cystic 4.7 cm submandibular gland mass.


Micro images:



What is your diagnosis?































Diagnosis:
Mammary analogue secretory carcinoma (with mammaglobin IHC)


Discussion:
Immunostains were obtained:

Mammaglobin



Mammary analogue secretory carcinoma (MASC) is a recently described salivary gland neoplasm characterized by its morphologic, immunophenotypic and molecular similarities to secretory carcinoma of the breast (Head Neck Pathol 2013;7:35). The vast majority arise in the parotid gland, and usually present as a slow growing, painless mass (Am J Surg Pathol 2010;34:599). MASC generally occurs in adults with mean age 47 years old, and there is a slight male predominance.

On gross examination, MASCs tend to be solitary and unencapsulated but well circumscribed. They may have a cystic component. The average size is 1.7 cm, and those arising in the oral cavity tend to be smaller (Head Neck Pathol 2013;7:35).

Histopathology shows variable architecture, with back to back tubules, papillae or microcysts. Secretions vary from light pink and frothy to brightly eosinophilic and colloid-like (Head Neck Pathol 2013;7:35). The tumor cells demonstrate granular, vacuolated eosinophilic cytoplasm and low grade nuclei (Am J Surg Pathol 2012;36:27). Mitotic rate is low and necrosis is absent. The cells are immunoreactive for S100, CK7 and mammoglobin. SMA and calponin are consistently negative, and, like secretory breast cancer, MASC is negative for ER and PR (Head Neck Pathol 2013;7:35). Both MASCs and secretory carcinoma have the t(12;15)(p13;q25), leading to a ETV6-NTRK3 fusion oncogene (Am J Surg Pathol 2012;36:27).

The most important differential diagnostic considerations are acinic cell carcinoma (AciCC), low grade cribriform cystadenocarcinoma and low grade mucoepidermoid carcinoma (Head Neck Pathol 2013;7 Suppl 1:S30, Am J Surg Pathol 2012;36:27). In contrast to AciCC, the cells of MASC are devoid of PAS+ secretory zymogen granules (Head Neck Pathol 2013;7 Suppl 1:S30). Molecular testing is now recommended to diagnose MASC (Head Neck Pathol 2013;7 Suppl 1:S30).

MASC is currently regarded as a low grade carcinoma with overall favorable prognosis, though the limited number of cases with complete clinical follow up data precludes exact assessment of its behavior. Potential for regional lymph node metastasis has been demonstrated. The tumor may recur locally, and in these cases adjuvant radiotherapy is recommended. High grade transformation has been reported, leading to metastasis and death (Virchows Arch 2015;466:245).


Discussion by Dr. Jennifer R. Kaley, University of Arkansas for Medical Sciences (USA).