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adenoid cystic carcinoma ( acc ) represents the second most common malignancy of the salivary glands and is associated with a poor long term prognosis .
one of the important prognostic factors is the histological grade determined by the percentage of solid component in the tumor [ 13 ] .
high grade transformation in acc is a recently defined entity , which is characterized by areas of conventional adenoid cystic carcinoma associated with concomitant presence of undifferentiated or poorly differentiated carcinoma .
however , this has not yet been included in the grading schemes for salivary acc .
only a few cases have been reported in the literature involving minor salivary glands and submandibular gland [ 410 ] .
we report the first case of acc with high grade transformation arising in the parotid .
a 54-year - old male presented at a tertiary care center of north india with complaints of a painful mass in the right infra - auricular region for 1.5  years .
the patient had noted a recent increase in the size of the mass and associated facial paresis for the last 2  months . on examination
, he had a hard mass in the right parotid with restricted mobility and facial nerve involvement .
fine needle aspiration cytology was performed , followed by surgical resection of the tumor , histological examination and immunohistochemical work - up .
formalin - fixed paraffin - embedded tissue was sectioned at 24  m and stained with hematoxylin and eosin .
the conventional adenoid cystic areas were graded according to the three tier grading system of szanto et al . .
primary antibodies used ( dako , denmark ) included cytokeratin ( ck ) and epithelial membrane antigen ( ema ) as markers of epithelial cell differentiation and s-100 and smooth muscle actin ( sma ) as markers of myoepithelial cell differentiation .
the markers to analyze the biological behavior of the tumor included cd117 , a c - kit proto - oncogene product , e - cadherin , a cell adhesion protein , her-2/neu , a transmembrane tyrosine kinase receptor and p53 protein , a tumor suppressor gene product .
p53 and ki-67 were assessed quantitatively in both the conventional acc and high - grade areas .
the reaction was visualized using the sensitive enzyme conjugated polymer - based detection system ( envision visualization system , dako , denmark ) .
the smears were stained with may grunwald giemsa , hematoxylin and eosin and papanicolaou stains .
formalin - fixed paraffin - embedded tissue was sectioned at 24  m and stained with hematoxylin and eosin .
the conventional adenoid cystic areas were graded according to the three tier grading system of szanto et al . .
primary antibodies used ( dako , denmark ) included cytokeratin ( ck ) and epithelial membrane antigen ( ema ) as markers of epithelial cell differentiation and s-100 and smooth muscle actin ( sma ) as markers of myoepithelial cell differentiation .
the markers to analyze the biological behavior of the tumor included cd117 , a c - kit proto - oncogene product , e - cadherin , a cell adhesion protein , her-2/neu , a transmembrane tyrosine kinase receptor and p53 protein , a tumor suppressor gene product .
p53 and ki-67 were assessed quantitatively in both the conventional acc and high - grade areas .
the reaction was visualized using the sensitive enzyme conjugated polymer - based detection system ( envision visualization system , dako , denmark ) .
the fine needle aspiration smears were cellular with dispersed and few non - cohesive clusters of atypical cells on a hemorrhagic background .
the atypical cells had intermediate to large , round to pleomorphic hyperchromatic nuclei , coarse chromatin , conspicuous nucleoli and variable amount of poorly defined cytoplasm .
differential diagnoses of adenocarcinoma ( not otherwise specified ) , undifferentiated carcinoma , salivary duct carcinoma , basaloid adenocarcinoma and carcinoma ex pleomorphic adenoma were entertained.fig . 
1fna smears showing dispersed population of highly pleomorphic cells with a small cluster of isomorphic basaloid cells surrounding a hyaline globule ( arrow ) ( mgg ) fna smears showing dispersed population of highly pleomorphic cells with a small cluster of isomorphic basaloid cells surrounding a hyaline globule ( arrow ) ( mgg ) on surgical resection , the tumor was vascular , encasing the facial nerve and infiltrating the subcutaneous tissue and adjoining fat planes . on gross examination ,
the tumor measured 5    4    2  cm and replaced the entire parotid except for a thin wedge of grossly uninvolved tissue at one side .
the cut surface of the tumor was variegated with solid , cystic , hemorrhagic and necrotic areas . on microscopic examination
the tumor was primarily composed of sheets and nests of cells with intermediate to large - sized hyperchromatic nuclei , prominent nucleoli , scant eosinophilic cytoplasm and frequent mitosis ( > 20/10  hpf ) ( fig .  2 ) .
a discrete focus of conventional adenoid cystic carcinoma ( grade ii ) occupying < 10% area of the studied sections was identified .
the tumor cells in this focus were arranged entirely in cribriform pattern showing small basaloid cells with interspersed pseudocystic spaces containing fuschinophilic acellular hyaline material and infrequent mitosis ( ~1/10  hpf ; fig . 
the tumor was diffusely infiltrating the adjoining salivary gland , fibrofatty tissue and skeletal muscle .
a single lymph node was identified in the attached fat , metastatic deposits in which showed presence of high grade areas along with few foci of conventional acc . a retrospective review of the fine needle aspirate smears revealed few small aggregates of isomorphic basaloid cells.fig . 
3conventional acc component with isomorphic basaloid cells in cribriform pattern ( upper left ) and high - grade undifferentiated acc component ( lower right ) high grade acc component showing pleomorphic undifferentiated cells with frequent mitoses ( arrows ) conventional acc component with isomorphic basaloid cells in cribriform pattern ( upper left ) and high - grade undifferentiated acc component ( lower right ) on immunohistochemistry the tumor was diffusely positive for cytokeratin , epithelial membrane antigen and s-100 in both the components .
smooth muscle actin was confined to the abluminal cells in the differentiated component but was negative in the high - grade component .
this was interpreted as presence of both epithelial and myoepithelial differentiation in the conventional acc areas , while there was loss of myoepithelial differentiation in the high grade areas .
p53 expression was seen in 20% tumor cells of conventional acc and was of moderate intensity .
however the high - grade component displayed strong nuclear p53 positivity in ~60% of tumor cells .
ki-67 staining showed a cell proliferation index of < 10% in conventional acc and 50% in the high - grade areas ( fig . 
e - cadherin and c - kit ( cd117 ) were positive in both the conventional and high - grade areas .
4nuclear positivity for ki67 ( arrows ) in greater proportion of cells in high - grade component ( lower right ) as compared to conventional component ( upper left ) ( dab ) nuclear positivity for ki67 ( arrows ) in greater proportion of cells in high - grade component ( lower right ) as compared to conventional component ( upper left ) ( dab ) a diagnosis of adenoid cystic carcinoma with high grade transformation was made .
five months of follow - up since surgery showed no recurrence or evidence of distant metastasis.table  1comparison of histology and immunohistochemical features in differentiated and high - grade componentsdifferentiated componenthigh grade componentrelative percentage1090histologyconventional acc grade iiundifferentiated carcinomarelative nuclear size124mitosis/10  hpf1>20ck , ema , s-100++sma+ ( abluminal cells)p53 intensitymoderate in 20% cellsstrong in 60% cellski67 index<10%50%her-2/neue cadherin++c kit++ comparison of histology and immunohistochemical features in differentiated and high - grade components
adenoid cystic carcinoma ( acc ) is an uncommon form of malignant neoplasm that arises most commonly in the major and minor salivary glands of the head and neck .
it is often slow to metastasize , but has a persistent and relentless growth with a poor long term prognosis .
major and minor salivary glands including seromucinous glands of upper respiratory tract are the frequent sites of occurrence .
, the tumor is composed of small uniform cells arranged in cribriform , tubular or solid growth patterns with interspersed globules and cylinders of hyaline basement membrane material .
have defined a three tier grading system which takes into account the histomorphologic pattern and percentage of the solid component .
first used the term  dedifferentiated adenoid cystic carcinoma to describe areas with pleomorphic tumor foci in close proximity to areas of conventional adenoid cystic carcinoma .
have reported eleven new cases with similar morphology and are proponents of the term  adenoid cystic carcinoma with high grade transformation. this encompasses tumors showing a high grade carcinoma with either a conventional low grade acc as described by cheuk , or a solid variant of conventional acc as described by sato et al . as the associated component [ 5 , 10 ] .
pubmed search revealed a total of 24 cases of dedifferentiated acc and acc with high grade transformation .
of these , 17 occurred in minor salivary glands of tongue , palate and sinonasal tract including a tumor in the hypopharynx [ 5 , 6 , 810 ] .
we report the first case from parotid . the parotid gland , though the commonest site of conventional acc has not been reported earlier as a site of high grade transformation of acc .
the transformed component showed prominent anisonucleosis , conforming to the criteria established by seethala et al . , requiring more than twofold nuclear enlargements as compared to the areas of conventional acc .
micropapillae and squamoid areas have been reported , but were not seen in our case [ 4 , 5 ] .
the cytological features of acc with high - grade transformation have not been reported earlier in the literature .
we considered the cytological differential diagnosis of adenocarcinoma ( not otherwise specified ) , undifferentiated carcinoma , salivary duct carcinoma , basaloid adenocarcinoma and carcinoma ex pleomorphic adenoma based on presence of a population of poorly differentiated atypical cells with occasional hyaline globules . on review , the aspirate smears were found to have small groups of basaloid cells , presumably derived from the conventional acc component .
it needs to be emphasized that a thorough analysis of fine needle aspirate smears in such cases may reveal groups of basaloid cells and hyaline globules amidst a highly pleomorphic population which would be pointers to a diagnosis of acc with high - grade transformation .
pre - operative aspiration diagnosis in such cases would be of value in deciding the extent of surgery and also promote thorough sectioning and sampling of tumor tissue received , since conventional acc areas may represent only a minor component . in our case ,
other studies have reported similar figures [ 4 , 5 , 7 , 9 ] .
immunohistochemical analysis revealed loss of myoepithelial markers in the high - grade component as reported in earlier studies [ 4 , 5 , 9 ] . the transformed component showed a ki-67 labeling index of 50% and p53 over - expression in 60% of tumor cells which was significantly greater than that in the conventional acc component .
similar findings have been reported earlier and attest to the morphologic picture as well as clinical outcome of such cases [ 5 , 710 ] .
c - kit was positive in both conventional and high - grade areas and did not help in discriminating between the two components as described in previous reports [ 4 , 5 , 7 , 9 ] .
e - cadherin expression , which has not been reported earlier , was seen in both the components .
previous studies have reported variable results of her-2/neu in the high grade component [ 4 , 9 , 10 ] .
her-2/neu negativity has been surmised as a helpful feature in ruling out the close differential of a hybrid acc - salivary duct carcinoma . in conclusion , we present the first report of adenoid cystic carcinoma with high - grade transformation arising in the parotid gland .
we emphasize that thorough study of aspirate smears may reveal clusters of basaloid cells and hyaline globules in a highly pleomorphic tumor cell population that may help to clinch a difficult differential diagnosis and guide extent of surgery and tissue sampling post - surgery .
higher p53 and ki67 expression in the high - grade component with associated loss of myoepithelial markers , suggest their possible role in pathogenesis .
adenoid cystic carcinoma ( acc ) constitutes about 4% of salivary epithelial tumors and is the second common malignant epithelial salivary gland tumor involving both the major and minor salivary glands . 
 high grade transformation in acc is a recently recognized entity with only a few cases reported in literature . 
 we report the first case of acc with high grade transformation involving the parotid . a 54-year - old man with a history of right parotid painful swelling from 1.5  years presented with recent increase in size of the swelling and facial paresis of 2  months duration . 
 the locally invasive salivary neoplasm was composed predominantly of an undifferentiated carcinoma with foci of conventional acc occupying less than 10% of tumor area . 
 immunohistochemical study of the undifferentiated component as compared to conventional acc showed greater over - expression of p53 and ki-67 . 
 her-2/neu was negative in both components . 
 recognition of occasional clusters of basaloid cells and hyaline globules in association with larger poorly differentiated malignant cell population in aspiration smears can help in cytological diagnosis . 
 the acquisition of high proliferation index and over - expression of p53 may be the probable factors involved in the pathogenesis of high grade transformation in a conventional acc .