acinic cell carcinomas ( acc ) are usually low grade , uncommon neoplasms constituting 2.54% of parotid gland tumors . papillary cystic variant ( pcv ) of acc is a rare tumor , the diagnosis of which is based on histopathological examination . it is composed of tumor with papillary and cystic growth patterns , with varying proportions of one or more cell types . it has mostly been reported in younger patients ( 16 - 40 years ) when compared to the classic type that characteristically presents in the fifth decade of life . although an uncommon tumor , it is important to recognize this variant as it has proved to be universally fatal within 10 years . we hereby report an unusual case of acc - pcv in a 20-year - old male which was considered a benign parotid mass both cytologically and radiologically . a 20-year - old male presented to the surgical clinic with a complaint of swelling on the left angle of mandible below the ear lobule since 4 months . it was 3.5 cm  2 cm in size , firm to hard with limited mobility and nontender . laboratory investigations revealed hemoglobin 16.2 gm% , total leucocyte count 6,800 cells/l , differential leukocyte count neutrophils 74% , lymphocytes 18% , eosinophils 5% , monocytes 3% , platelet count - 1.15 lac/l and blood sugar 120 mg / dl . contrast - enhanced computed tomography of neck showed a soft tissue nodular lesion isodense to the parotid ( attenuation 40 hu ) of size 2.3 cm  1.6 cm  1.3 cm with mildly enhancing peripheral walls in the left superficial parotid gland . few spiculated nodules were also seen in the right lung apart from patches of numerous centriacinar nodules . both lobes of the thyroid were normal in size , shape , attenuation and enhancement . grossly , the specimen measured approximately 6.5 cm  4.5 cm  3.5 cm with attached flap of skin measuring 3.5 cm  1.5 cm . cut surface showed a large cyst measuring 2.8 cm  1.5 cm filled with dark brown material [ figure 1 ] . histopathological examination showed a large well - circumscribed cystic space lined by numerous papillary projections few of them showing thin vascular cores [ figure 2 ] . many hemosiderin - laden macrophages and areas of hemorrhage are also seen [ figure 3a ] . these papillae were mostly lined by hobnail cells with round , vesicular nuclei , central nucleoli and eosinophilic to vacuolated cytoplasm [ figure 3b ] . gross specimen cut surface of which shows a large cyst measuring 2.8 cm 1.5 cm filled with dark brown material numerous papillae lying in cystic cavity ( black arrow ) , fibro collagenous tissue and adjacent normal salivary gland tissue ( white arrow ) ( a ) papillary growth pattern along with hemosiderin within the papillae . acinic cell carcinoma is an uncommon salivary gland tumor , making up 1% of all salivary gland neoplasms . they most often arise in the parotid gland , but may occasionally involve the submandibular , minor salivary or seromucinous glands . it is the least aggressive of salivary gland cancers with low malignant potential , but several recurrences and metastasis have been reported . few high - grade variants of acc are known such as papillocystic carcinoma or carcinomas with undifferentiated cells in the medullary pattern . lesions of the  tail  of the parotid gland are difficult to assess clinically and provide a diagnostic dilemma on imaging . most benign parotid tumors present as slow - growing , painless masses often in the tail of the parotid gland . defines the  tail  of the parotid gland as inferior 2 cm of the superficial lobe of the gland . in a study by hamilton on 117 parotid tail masses , seventeen types of parotid tail masses were identified out of which benign lesions were the most common . also as it was a slow - growing painless mass present in the parotid tail , clinically it was thought to be a benign parotid mass which was also supported by cytological examination . accurate localization of these lesions on imaging is essential to assist the clinical diagnosis and to prevent inadequate / incomplete excision and complications , especially damage to the facial nerve . the diagnosis of pcv of acc usually poses a challenge because of the cytoarchitecture that is different from classic type . cystic fluid in the case of acc - pcv dilutes the overall cellularity leading to a mistaken diagnosis of benign lesion as was seen in the present case . histopathologically , acc shows a myriad of architectural patterns : solid , solid - lobular , acinar - microcystic , papillary cystic , tubuloductal , follicular and macrocystic , and dedifferentiated . the solid and microcystic are the most common subtypes and the pcv accounts for one - fourth of acc . varying proportions of one or more of five cell types are seen including hobnail , acinar , intercalated , vacuolated , nonspecific glandular and clear cells . this is due to bulging of the apical portions of lumen lining cells into the lumen presumably after release of secretions . the clinical picture is not specific , and diagnosis is based on the histopathologic examination . the mean age of occurrence is in the fifth decade , but the pcv is reported to occur in younger patients compared to the classic type . the most significant differential diagnosis of acc - pcv is papillary carcinoma of the thyroid . thyroid ultrasonography , hormonal assays , and immunohistochemistry for thyroglobulin are helpful in differentiating these two lesions . timely diagnosis and treatment of acc - pcv is essential as it has been found to be universally fatal within 10 years . although most parotid masses are benign , removal is required for histopathologic confirmation because of the clinical and radiologic overlap . to conclude , the present case emphasizes the importance of histopathological examination in parotid masses as the imaging features as well as cytology lack the necessary specificity to differentiate benign from malignant masses , especially in a case of papillary cystic acc . it also highlights the need to consider malignant lesion in the differential diagnosis of parotid tail tumor .