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since 2010 when the seminal paper by sklov et al . was published , many authors have begun to catalog the diagnosis and clinicopathologic characteristics of mammary analogue secretory carcinoma ( masc ) . however , while the literature concerning the histological characteristics of masc is burgeoning , the cytomorphological features of masc and its addition to the differential diagnosis of a salivary gland fine - needle aspiration ( fna ) specimen by cytopathologists is just emerging . until date , few cases of masc sampled by fna have been reported ; with one lesion diagnosed via cytological analysis ( the remaining cases received a final diagnosis of masc after histological evaluation ) . here
the case we present here is about a 51-year - old female who presented with an asymptomatic parotid mass found on routine examination . computed tomography scan showed a hyper - attenuating 0.8  0.7 cm lesion in the superficial lobe of the right parotid gland , which was confirmed on magnetic resonance imaging .
the patient underwent fna at an outside institution and a diagnosis of  consistent with pleomorphic adenoma ( pa )  was rendered .
the fna slides were reviewed at our institution for surgical management ( notably the diff quick preparation from the outside institution was of poor quality ) .
the fna specimen showed a monomorphic population of lesional cells arranged in papillary groups with transgressing vessels [ figure 1 ] .
the lesional cells demonstrated round nuclei , prominent nucleoli and foamy cytoplasm [ figure 2 ] .
salivary gland neoplasm , low grade  with differential diagnosis of acinic cell carcinoma ( acicc ) and low grade mucoepidermoid carcinoma ( mec ) .
fine - needle aspiration cytology smear demonstrating a monomorphic population of cells with eosinophilic cytoplasm arranged in papillary groups ( papanicolaou , 40 ) fine - needle aspiration cytology smear demonstrating lesional cells with round nuclei , prominent nucleoli and foamy cytoplasm ( papanicolaou , 60 , inset , 100 ) the patient subsequently underwent resection and the mass was received for histological evaluation .
the lesion appeared as a well circumscribed gray - tan nodule within the superficial parotid gland , measuring 0.8 cm in greatest dimension .
the histological examination displayed a circumscribed , unencapsulated lobulated mass with microcystic and tubular structures [ figure 3 ] .
the tumor cells had pale eosinophilic granular cytoplasm and low grade nuclei with distinct nucleoli [ figure 4 ] .
focal invasion of the surrounding parotid gland was noted ; however no perineural invasion or lymphovascular invasion was identified .
a mucicarmine stain was negative , while periodic acid schiff with and without diastase failed to demonstrate intracytoplasmic glycogen , and highlighted secretory material in microcystic spaces .
as masc was suspected , this material was tested for etv6 rearrangement by fluorescence in situ hybridization ( fish ) , which demonstrated an atypical etv6 rearrangement in 167/200 cells ( 83% ) , confirming the diagnosis .
histologically , the tumor is a circumscribed , unencapsulated lobulated mass with microcystic and tubular structures ( h and e , 2.5 ) histologically , the microcystic structures contain bubbly , eosinophilic secretions ; the tumor cells have pale eosinophilic granular cytoplasm and low grade nuclei with distinct nucleoli ( h and e , 40 )
mammary analogue secretory carcinoma , first described in 2010 , is a newly recognized neoplasm of the salivary gland .
as its name implies , it shares morphologic and cytogenetic characteristics with its counterpart in the breast . occurring most commonly in the parotid , masc is a low grade neoplasm often confused with acicc , particularly the  granular poor  variant . unlike acicc , masc is strongly positive for s100 and mammoglobin and negative for dog-1 .
masc also differs from acicc in its clinical presentation , occurring more commonly in males , frequently associated with lymph node metastases , and is thought to be more common in extra - parotid sites .
this tumor harbors a unique translocation , t(12;15 ) ( p13;q25 ) that results in the fusion of etv6 with ntrk3 , which produces a transformative chimeric tyrosine kinase .
although present in several pathologic processes , if identified , this translocation is thought to be diagnostic of masc in the appropriate pathologic setting .
cytologically , masc is often confused with other oncocytic salivary gland tumors , including primarily acicc and mec , but also can rarely be misclassified as salivary duct carcinoma ( sdc ) and pa .
similar to the cases in the current literature , our case demonstrated a monomorphic population of lesional cells forming papillary groups with transgressing vessels .
the individual cells demonstrated round nuclei with prominent nucleoli and abundant , eosinophilic foamy cytoplasm .
overall , the appearance was that of a low grade tumor , as pleomorphism and mitotic figures were not noted . while masc and acicc can have similar architectural patterns
, masc may show evidence of mucin production , a feature not seen in acicc .
furthermore , according to some authors , masc is more likely to demonstrate greater variation in the size of cytoplasmic vacuoles .
when compared to mec , particularly the oncocytic variant , masc can share features of mucin production and eosinophilia . however , architectural patterns such as papillae with transgressing vessels are more characteristic of masc and cells tend to have multivacuolation , as opposed to the univacuolation reported in cases of mec .
sdc often will exhibit nuclear pleomorphism and tumor diathesis , revealing its high grade nature and distinguishing it from masc . in those rare cases that appear less clearly malignant ,
sdc will still often demonstrate greater size variation and decapitation secretions ( cell block ) .
although on the other end of the neoplastic spectrum of sdc , pa can also rarely be confused with masc ( as occurred originally in the present case ) .
the mucin production in masc may be so abundant as to be confused with the myxoid stroma of pa .
however , in most cases it should be clearly distinguishable from the metachromatic material seen in pa .
the key , and often present , features include the papillary architecture and distinct granular cytoplasm seen in cases of masc .
though , based on cytomorphology alone , the definite diagnosis can be challenging , in conjunction with available clinical clues ( i.e. , male patient , extra - parotid site ) masc should be included in the differential diagnosis of fna specimens diagnosed as oncocytic salivary gland neoplasms or suspicious for acicc .
this creates an opportunity for ancillary studies such as immunohistochemistry and/or fish analysis on cell block material , which may lead to the appropriate classification of the lesion prior to surgical resection .
all authors of this article declare that we qualify for authorship as defined by icmje http://www.icmje.org/#author .
each author has participated sufficiently in the work and take public responsibility for appropriate portions of the content of this article .
tds , val and zb were each directly involved in the diagnosis of this case .
as this is case report without identifiers , our institution does not require approval from institutional review board ( irb ) ( or its equivalent ) .
to ensure the integrity and highest quality of cytojournal publications , the review process of this manuscript was conducted under a double - blind model.(authors are blinded for reviewers and vice versa ) through automatic online system .
mammary analogue secretory carcinoma ( masc ) is a newly recognized neoplasm of the salivary gland , first described in 2010 . 
 this tumor harbors a unique translocation , t(12;15)(p13;q25 ) that results in the fusion of etv6 with ntrk3 which produces a transformative chimeric tyrosine kinase . to date , few cases of masc sampled by fine needle aspiration have been reported . 
 cytologically , masc can be confused with other oncocytic salivary gland tumors , including warthin - tumor , acinic cell carcinoma ( acicc ) and mucoepidermoid carcinoma . 
 it is characterized by a monomorphic population of lesional cells with round nuclei , prominent nucleoli and abundant , eosinophilic foamy cytoplasm ; forming papillary groups with transgressing vessels . 
 though , based on cytomorphology alone , the definite diagnosis can be challenging , in conjunction with available clinical clues ( i.e. male patient , extra - parotid site ) masc should be included in the differential diagnosis of fna specimens diagnosed as oncocytic salivary gland neoplasms or suspicious for acicc . here 
 we present a case of masc with fna sampling at our institution .