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tumors of salivary glands constitute a heterogeneous group of lesions of great morphologic variation . annual incidence of salivary gland tumors around the world is 1 - 6.5 cases per 100,000 people .
they are more common on hard palate than soft palate , probably because there are greater number of gland aggregate on hard palate than on soft palate .
cystadenomas of salivary glands are benign neoplasms , in which the epithelium demonstrates adenomatous proliferation that is characterized by formation of multiple cystic structures .
several morphological variants of cyst adenoma have been described of which papillary and mucinous cystadenoma are important .
world health organization ( who ) described papillary cystadenoma which closely resembles wartins tumor , but without the lymphoid elements .
if mucous cells predominate in the cell population of the lining epithelial cells , the tumor is termed as mucinous cystadenoma .
cystadenoma is a rare , slowly and painlessly enlarging asymptomatic salivary gland tumor that rarely exceeds 1.5 cm in diameter and most commonly occurs in the minor salivary glands .
common sites of occurrence are palate and buccal mucosa , lip and the tonsillar area , but cyst adenomas have also been reported to occur on the tongue .
recurrence may result from incomplete excision of the slow - growing cyst adenoma or when a cystadenocarcinoma is mis diagnosed .
the use of a carbon dioxide laser has become common in oral and maxillofacial surgery for lesions of the oral mucosa .
advantages reported for the carbon dioxide laser in oral soft - tissue surgery include , minimal damage to adjacent tissue , good hemostasis , minimal inflammatory reaction , scar formation and precise cutting .
a 60-years - old female reported with an asymptomatic swelling in the right posterior palatal area in the region of missing 15,16 and 17 [ figure 1 ] .
the swelling was present since several months and gradually increased to the presenting size . on examination ,
a well - defined , round mass , approximately 2 cm in diameter was revealed , which was soft to firm in consistency , non - movable , slightly compressible and painless .
no carious tooth was found to be associated and there was no sign of tooth displacement .
swelling in the right posterior palatal region a provisional clinical diagnosis of benign minor salivary tumor was given for differential diagnosis , pleomorphic adenoma , a low- grade minor salivary gland malignancy acinar cell adenocarcinoma ( acac ) , adenoidcystic carcinoma , mucoepidermoid carcinoma ) , residual cyst , retention phenomenon , lipoma , neurofibroma and palatal odontogenic keratocyst were considered .
patient was investigated with a panoramic and a maxillary occlusal radiograph , which showed no bony alteration in the area of the swelling .
h and e stained smear of the aspirate showed presence of mostly red blood cells and some chronic inflammatory cells .
routine hematological investigations were advised before the patient was referred to oral surgery for excision of the palatal mass .
the lesion was excised completely along with the nerves and vessels under local anesthesia by raising a mucosal flap [ figure 2a ] and a single soft - tissue bit of about 2 cm  1.6 cm [ figure 3 ] was sent for histopathological examination .
primary closure of the overlying mucosa was performed [ figure 2b ] and the wound healed by primary intention without any intra - or post - operative complications [ figure 2c ] .
surgical excision by raising a full thickness mucosal flap ( a ) , primary closure of the wound ( b ) , post - operative : healing after 1 month ( c ) soft - tissue bit sent for histopathology ( approx .
1.6 cm  2.0 cm ) the histopathological examination revealed numerous large and small cystic spaces interspersed in a fibrous connective tissue stroma [ figure 4 ] .
the cystic lumens were lined by 1 - 3 cell layer thick epitheliums , which varied from flattened to cuboidal to tall columnar cells [ figure 5 ] .
the stroma exhibited multiple hemorrhagic areas and focal aggregates of chronic inflammatory cells along with few mucous cells .
normal appearing mucous acini could also be appreciated in the deeper sections [ figure 6 ] . cellular atypia and mitosis were absent .
photo micrograph depicting large and small cystic spaces ( black arrows ) in moderately fibrous connective tissue stroma along with numerous hemorrhagic areas ( h and e , 40 ) photo micrograph depicting cystic lumen with flat ( a ) and cuboidal ( b ) epithelial lining ( black arrows ) .
( h and e , 40 ) ( a)photo micrograph showing normal appearing mucous acini ( black arrow ) ( h and e , 100 ) ; photo micrograph .
( b ) showing layer of epithelial cells(white arrow ) lining a cystic cavity with foamy mucous secretion on the surface ( h and e , 40 )
cyst adenoma is a rare benign neoplasm of epithelial origin found chiefly affecting the minor salivary glands .
although cases involving the major salivary glands have been reported . who , in its revised classification in 1992 , sub - classified cyst adenoma into two distinct histopathological varieties - mucinous and papillary .
alexis and dembrow reported the incidence of cyst adenoma to be 2% of all minor salivary gland tumors and 4.7% of benign epithelial salivary gland tumors .
waldron et al . reported a higher rate of occurrence of 4% and 8.1% of all the minor salivary gland tumors and of all benign epithelial salivary gland tumors respectively .
reported 2% cases of cyst adenoma out of 800 intra oral minor salivary gland tumors .
bauer and bauer suggested that the cyst adenoma arises principally from the undifferentiated epithelium of the intercalated ducts of the salivary gland .
the papillary variety of cyst adenoma exhibits papillary proliferations that project into the cystic lumens and may closely resemble the warthin 's tumor with the absence of the lymphoid element .
the less frequently seen mucinous variety predominantly shows mucous cells in the epithelial lining of the cystic lumens , with absence of distinctly visible papillary projections .
cyst adenoma has been reported to occur in patients between 17 years and 86 years of age with a mean age of about 61years .
it frequently occurs in the 6 decade of life more frequently in females , with a female : male ratio being 3:1 .
the age of occurrence in our case is in terms with what has been reported in the literature .
the most common site of occurrence is the palate , as described in our case , followed by the buccal mucosa and the tongue .
it has also been reported to occur on the upper and lower lip and floor of the mouth .
mucinous cyst adenoma of minor salivary gland of the nasal fossa has been reported by cano cuenca et al .
as such , cystadenoma presents no distinct clinical features and may be impossible to differentiate clinically from other benign salivary gland tumors , mucous retention or extra vasations phenomena and low - grade minor salivary gland malignancies such as papillary cystic variant ( pcv ) of acc , adenoid cystic carcinoma and muco epidermoid carcinoma .
acinic cell carcinoma although is considered a low grade malignancy with a 5 year survival of 90% , but its papillary variety ( acc - pcv ) has been reported to be universally fatal in 10 years .
papillary folds are seen interspersed with cystic spaces , which may be small or large with well - defined papillary growths and glandular epithelial masses stranded by cords of fibro vascular tissue .
multiple vacuolated and acinar cells may also be seen along with hob nailing or tomb stoning of luminal cells , which is characteristic of acc - pcv . however , the reported case is of the mucinous variety of cyst adenoma typically showing absence of papillary projections within the cystic lumen .
further , acc - pcv is reported to occur in younger patients ( 16 - 40years ) , contrary to our case of a 60-year - old female .
when cystadenoma occurs on the palate , such as in our case , it must be differentiated from radicular/ residual cyst and palatal space abscess and a possible odontogenic origin must be ruled out by necessary radiographic examination .
the histopathological features described in our case were characteristic and in general agreement with what has been reported in the literature for cystadenoma.25% cases of cystadenoma have been reported to show a distinct fibrous capsule , which was not present in our case .
since salivary gland tumors show great histomorphological diversity , differential diagnosis of cystadenoma must include intra ductal papilloma , cystadeno carcinoma , low - grade mucoepidermoid carcinoma and warthin 's tumor .
most cases of cystadenomas , including our case , are treated by simple surgical excision .
regular follow - up of the patient is necessary for early identification of recurrence , which may occur due to incomplete excision . to the best of authors
knowledge , very few cases have been reported of mucinous variety of cystadenoma and that too at extra oral sites .
the aim of this case report is to document the rarely reported mucinous cystadenoma and may be the first reported mucinous cystadenoma in the oral cavity among the indian population .
cystadenoma is a rare benign salivary gland tumor that chiefly originates in the minor salivary glands as a cystic growth with papillary projections into the cystic lumen without the lymphoid element . 
 it is further classified into two histopathological variants that have been recognized by world health organization as the papillary and the mucinous forms of cystadenoma . 
 clinically , it is difficult to differentiate from other benign minor salivary tumors and mucous retention phenomenon . 
 diagnosis is chiefly based on characteristics histological features . 
 it is believed that the salivary gland tumors are difficult to diagnose and interpret because there are varied patterns of presentation . 
 the study of salivary gland disorders has increased in leaps and bounds . 
 the authors report a case of mucinous cystadenoma of the minor salivary gland on the hard palate , which is even rarest of the rarely reported cystadenomas of the minor salivary glands .