basal cell adenomas are unique benign salivary gland tumors affecting women over 50 years of age comprising 13% of all salivary gland tumors . cytologically , they mimic several benign and malignant salivary and non - salivary gland tumors , warranting thorough histopathological examination . we describe basal cell adenoma in a young man with emphasis on cytological features and differential diagnoses . a 22-years - old man presented with a lump behind the left ear of 5 months duration . clinical examination showed a nodule behind the left ear measuring 1.5  1.5 cm in size [ figure 1a ] . there was no history of fever , weight loss , cough or tenderness . with a clinical diagnosis of salivary gland tumor cytological smears showing ( b ) basaloid cells in nests sheets and trabeculae ( pap stain ; 100 ) . ( c ) peripheral palisading of cells ( red arrows ) and bare nuclei in background ( pap , x400 ) ) ; ( d ) basement membrane material around cell clusters ( green arrows ) ( pap , x400 ) the aspiration yielded haphazardly arranged clusters and sheets of basaloid cells with scanty to moderate cytoplasm having round - oval benign nuclei with fine chromatin and indistinct nucleoli . numerous bare nuclei were seen in the background . a thin peripheral ribbon of basement membrane material and peripheral palisading was present in some clusters . squamous morules , hyaline globules , stromal elements , inflammatory cells , pleomorphism , mitoses and necrosis were absent [ figure 1b  d ] . with a cytodiagnosis of basaloid neoplasm probably benign , excision of the lesion was suggested as several tumors like basal cell adenoma , basal cell adenocarcinoma , canalicular adenoma , cellular pleomorphic adenoma and solid variant of adenoid cystic carcinoma needed to be excluded in the differential diagnosis . intraoperatively , it was decided to limit the surgery to simple excision of nodule as the tumor was well encapsulated , lacked extensions outside the capsule and could be easily enucleated . the surgical specimen consisted of a nodular , well encapsulated , solid tumor measuring 2  1.5 cm with a homogenous lobulated cut surface [ figure 2a ] . histopathology showed a well - encapsulated benign tumor composed of uniform bland basaloid cells with round to oval nuclei and scant cytoplasm arranged in tubules , nests , trabeculae and sheets separated by collagenous non mucoid stroma . peripheral palisading of cuboidal cells was observed in occasional tumor nests [ figure 2b and c ] . capsular / vascular invasion , neurotropism , pleomorphism , necrosis and cystic change were absent . thus , a final diagnosis of basal cell adenoma , tubulo - trabecular type , was made . ( a ) gross examination : tumor with a solid homogenous grey - white lobulated cut surface . ( b - d ) histological sections showing basaloid cells with uniform round - oval nuclei , eosinophilic cytoplasm and indistinct cytoplasmic borders arranged in tubulo - trabecular pattern separated by collagenous stroma and peripheral palisading within the nests . ( h&e stain , ( b ) x200 , ( c ) x400 , ( d ) x400 ) basal cell adenoma is an uncommon benign basaloid salivary gland neoplasm rarely seen in the young . cytologically small basaloid type of epithelial cells with bland oval nuclei , fine chromatin , indistinct nucleoli arranged in sheets , trabeculae and nests along with bare nuclei are seen . two populations of cells may be seen ; cells with larger nuclei and moderate cytoplasm and a second population with dark nuclei and scant cytoplasm . peripheral palisading and amorphous homogenous basement membrane material around the nests and hyaline globules may be found . four histological patterns of basal cell adenoma are observed : solid ( sheets of basaloid cells separated by collagenous stroma ) , trabecular ( nests and cords of basaloid cells separated by cellular stoma ) , tubular ( glandular formations ) and membranous ( thick bands of hyaline material at the periphery of basaloid cells ) . basal cell adenocarcinomas are low grade malignant tumors of the elderly with low risk of metastasis and recurrence and are hence treated by radical surgery . histologically they show basaloid cells in sheets and trabeculae , mitotic activity of more than four per high power field , nuclear pleomorphism , vascular and perineural invasion and infiltration of adjacent normal structures . immunohistochemistry ( ck7 , smooth muscle actin , ki67 ) can not distinguish between benign and malignant basaloid neoplasms . adenomas mimic basal cell adenomas cytologically but histologically show columnar epithelial cells in thin anastomosing cords with beaded pattern . they involve minor salivary glands of the oral cavity and have similar prognosis and therapeutic guidelines as basal cell adenomas . cellular pleomorphic adenomas , ( like the classical type ) may recur after incomplete excision , requiring lobectomy . cytologically they show basaloid cells , fibrillary / myxoid material with spindled and plasmacytoid cells in the background . histological examination of the lesion is essential to identify the stromal component as myxoid material may be absent in cytological smears . cytologically , they show pleomorphism , increased mitosis , necrosis apart from basaloid cells and hyaline globules . histological evidence of vascular or perineural invasion , infiltration of adjacent normal structures and ki 67 index of more than 5% differentiate them from basal cell adenoma . cytokeratin 5/6 , p53 , cd117 , s100p protein and nuclear beta catenin are used to differentiate them from other basal cell neoplasms . basaloid squamous cell carcinomas are aggressive tumors of the aerodigestive tract , treated by radical surgeries and radiotherapy or chemotherapy . cytologically , they show basaloid cells with marked nuclear pleomorphism , necrosis , focal keratinization and infiltrative growth on histology . cytologically , cutaneous cylindromas overlying the salivary glands show hyaline globules and basaloid cells , however they can be distinguished by careful clinical examination . all variants of basal cell adenomas are treated by local excision or resection of involved lobe except the membranous type which requires extensive surgery due to increased recurrence rate ( 24% ) . our case was tubulo - trabecular type of basal cell adenoma and hence , restricting the surgery to excision of nodule was justified . we present a unique case of basal cell adenoma of the parotid in a young male . hence , histopathology is mandatory for accurate diagnosis , tumor subtyping and correct surgical management . this case report aims to create awareness about the various cytological differentials of basaloid neoplasm , the pitfalls in cytodiagnosis of these tumors and their impact on management .
basal cell adenoma ( bca ) is a rare benign epithelial tumor of the salivary gland , displaying monomorphic basaloid cells without a myxochondroid component , representing 13% of all salivary gland neoplasms seen predominantly in women over 50 years of age . 
 it is uncommon in young adults . 
 cytodiagnosis of basaloid tumors chiefly basal cell adenoma of the salivary gland , is extremely challenging . 
 the cytological differential diagnoses range from benign to malignant , neoplastic to non- neoplastic lesions . 
 histopathological examination is a must for definitive diagnosis , as these entities differ in prognosis and therapeutic aspects . 
 we present a 22-years - old male with this uncommon diagnosis with a discussion on the role of cytological diagnosis . 
 fine needle aspiration cytology is a simple , minimally invasive method for the preoperative diagnosis of various types of neoplastic and non - neoplastic lesions . 
 the knowledge of its pitfalls and limitations contributes to a more effective approach to treatment .