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the term  adenoid cystic carcinoma  ( acc ) was first used by spies in 1930 .
it is more common in the minor salivary glands ( > 25% ) rather than in the major salivary glands ( about 5% ) .
the tumor is characterized by slow and relentless growth with a tendency for extensive local invasion .
a particular feature of acc is the tumor 's propensity for perineural invasion that may result in the spread along the involved nerves .
a few point mutations in known cancer genes , including kras , braf and tp53 have been reported in accs .
recently , recurrent translocation t ( 6;9)(q22 - 23;p23 - 24 ) was identified resulting in the fusion of the v - myb myeloblastosis viral oncogene homolog ( myb ) gene on chromosome 6 to the nuclear factor i / b gene on chromosome 9 in a major number of cases .
however , the extent to which other genes contribute to the disease is not well understood .
most commonly followed the method of treatment for acc seems to be surgical resection combined with radiotherapy . a 64-year - old man presented to the department of oral medicine and radiology with a 3-month history of swelling in the right anterior floor of the mouth .
the patient had noted reduced salivation for 2 months along with a little discomfort in speech and mastication due to the size of the tumor .
extra - oral examination revealed a palpable right submandibular lymph node measuring around 2 cm  2 cm in size , tender and soft in consistency suggestive of an inflammatory nature of the lesion .
intra - oral examination revealed a tender , solitary , soft , and sessile swelling in the right anterior floor of the mouth measuring about 3 cm  2 cm extending mesiodistally from central incisor to premolar region and superioinferiorly from the depth of the lingual vestibule to the level of occlusion .
examination also revealed an ulcer over the swelling [ figure 1 ] . considering the history of reduced salivation and discomfort in mastication , provisional diagnosis of submandibular salivary sailolith and ranula was considered . 

figure 164-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
intraoral photograph shows smooth surface with well - defined borders ( solid arrow ) . 
 
64-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
acc may require ultrasonography ( us ) , computed tomography ( ct ) , and magnetic resonance imaging ( mri ) for evaluating perineural , vascular , or skull base infiltration .
the limitation of us includes its inability to evaluate the deep lesions . because ct is less accurate than mri for detecting the extent of disease , mri is preferred over ct . in case of bone pain ,
acc is best evaluated by using t1-weighted and fat - suppressed t2-weighted and gadolinium enhanced mri .
the lesion exhibits homogenous hypointense signals with ill - defined margins on t1-weighted mri and after injecting gadolinium intravenously acc shows continuous rapid or gradual enhancement pattern . on t2-weighted mri ,
low signal intensity corresponds to the solid type with poor prognosis and high signal intensity corresponds to either the cribriform or tubular subtypes with better prognoses .
mandibular cross - sectional occlusal radiograph of the 64-year - old patient showed no identifiable sailoliths [ figure 2 ] .
the patient 's socioeconomic status did not allow use of the more expensive diagnostic imaging modalities . with a provisional diagnosis of ranula , surgical excision of the swelling
figure 264-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
64-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
the swelling was found to begin from the sublingual duct and to obstruct the submandibular duct [ figures 3 and 4 ] .
histological investigation of the excised tissue stained with hematoxylin and eosin revealed basaloid epithelial cells arranged in cyst like spaces ( duct like appearance ) , with many of the spaces presenting with hyalinized and mucoid appearance .
the cells appeared small and uniform with deeply basophilic nuclei and a predominently cribriform architecture suggestive of acc arising from the right sublingual gland [ figure 5 ] .
considering the patient 's age and socioeconomic status , no further investigations or radiotherapy was done .
patient was advised to return for a follow - up examination once in 3 months because of the relentless growth of acc which has a tendency for extensive local invasion .
figure 364-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
figure 464-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
figure 564-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
photomicrograph of the hematoxylin and eosin stained tissue ( 10 ) shows multiple basaloid epithelial cells with isomorphic and basophilic nuclei arranged in cribriform architecture ( solid arrow ) . 
 
64-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
64-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
64-year - old - male with swelling in the right anterior floor of the mouth diagnosed with adenoid cystic carcinoma .
photomicrograph of the hematoxylin and eosin stained tissue ( 10 ) shows multiple basaloid epithelial cells with isomorphic and basophilic nuclei arranged in cribriform architecture ( solid arrow ) .
accs may show any one of the following patterns : solid , trabecular , tubular , and cribriform . among these cribriform type is the most common variant .
cribriform form shows the presence of extensive sheets , uniform bands and is composed of small , darkly stained , slightly separated basal cells with duct like structures , which may contain secretory products .
the present case showed the most common cribriform pattern of acc . according to many authors histological subtype influence the prognosis of the disease .
histological subtypes of tubular and cribriform acc have a better prognosis than lesions with trabecular and solid patterns .
acc of the sublingual salivary gland causing obstruction of the submandibular duct is exceedingly rare : only three cases have been reported in the literature .
the peak incidence is seen during the fifth and sixth decades of life and shows a female predominance .
most of the patients with acc present with a mass , which has been there for months or years .
pain is felt by a few patients and is more often associated with advanced or recurrent tumors . in the present case , a 64-year - old - male patient presented with swelling of only 3-months duration and experienced mild pain , which may be associated with traumatic ulceration on the swelling rather than due to the tumor itself .
possible treatment modalities of acc include surgical therapy , radiotherapy , chemotherapy , and combined therapy .
post - operative radiotherapy is indicated for tumors associated with perineural spread , local recurrence , and distant metastases . according to avery et al .
alcedo et al . , opened up a new possibility in the pharmacological treatment of this tumor by demonstrating its response to imatinib mesylate , a potent inhibitor of kit tyrosine kinase , an enzyme involved in the pathogenesis of this tumor .
several genomic investigations have been carried out in accs to identify biological markers of therapeutic potential .
these efforts , however , have been largely unrewarding and more investigations of new targets are needed . in the present case , only surgical therapy was preferred and further management was not done due to patient 's socio - economic status . in spite of only surgical management , 9-month follow - up showed no recurrence
. this may be due to better prognosis associated with the less aggressive cribriform type of the lesion .
further studies are required to validate treatment with only surgery in cases of tubular and cribriform forms of accs .
acc of sublingual glands is rare and tumors causing obstruction to submandibular duct are extremely rare .
review of the literature shows that until date , only three cases have been reported . us ,
ct , and mri are helpful tools in the diagnosis of accs . the diagnosis can be confirmed and the subtype identified by histological investigations . most common method of treatment for acc seems to be surgical resection combined with radiotherapy .
the present case was managed only with surgical modality and 9-month follow - up showed no recurrence .
long - term follow - up and newer biological markers of therapeutic potential are necessary to validate use of only surgery to manage tubular and cribriform accs .
sublingual salivary gland malignancies are extremely rare and account for only 0.3 - 1% of all epithelial salivary gland tumors . here , we report a case of adenoid cystic carcinoma ( acc ) of the sublingual salivary gland that presented as a swelling in the right anterior floor of the mouth obstructing the submandibular duct . 
 sublingual salivary gland acc obstructing the submandibular duct is rare and only three cases have been reported in the literature until date . 
 we discuss the different patterns of acc seen during the pathologic investigations and its radiologic features .