adenoid cystic carcinoma ( acc ) is an epithelial malignancy and constitutes 810% of all salivary gland tumors . they arise from the minor or major salivary glands with intracranial spread through perineural , hematogenous , or contiguous extension . the hematogenous spread is the least commonly reported , especially from an unknown primary with only 13 cases having been reported in available literature . a 35-year - old gentleman presented with clinical features suggestive of raised intracranial pressure lasting for 2 weeks . on clinical examination , he was conscious and oriented . on general physical examination , he had no palpable swelling anywhere else in the body . cranial computer tomography ( ct - plain and contrast ) revealed a right parieto - occipital mass lesion . it was isodense on plain scan with an area of hyperdensity situated posteriorly , suggesting calcification . the lesion was enhancing heterogeneously on contrast with significant perilesional edema [ figure 1a ] . magnetic resonance imaging of the brain ( plain and contrast ) revealed a lesion , which was iso- to hypo - intense on t1-weighted and iso- to hyper - intense on t2-weighted . lesion was again enhancing heterogeneously on contrast and measured 5.2 cm  4.4 cm  4.2 cm [ figure 1b and c ] . peroperatively , the lesion was found to be grayish white , firm to hard , and highly vascular . ( a ) cranial computer tomography ( postcontrast ) revealing a right parieto - occipital mass lesion , enhancing heterogeneously on contrast with significant perilesional edema . ( b and c ) magnetic resonance imaging of the brain ( plain and contrast ) revealing a lesion , isointense to hyperintense on t2-weighted ( b ) with heterogeneous enhancement on contrast measuring 5.2 cm  4.4 cm  4.2 cm ( c ) . ( d ) computed tomography ( postcontrast ) 18 months no residual lesion histopathological examination revealed a neoplasm which was sharply demarcated from surrounding normal parenchyma by reactive gliosis [ figure 2a ] . the tumor cells were arranged in tubular and cribriform pattern [ figure 2b  d ] , at places forming ductular structures [ figure 2b ] lined by stratified cuboidal cells . the tubules and acini contained hyaline [ figure 2c ] or mucinous material [ figure 2d ] . the hyaline material was seen both surrounding the tubules as well as within the tubules . the tumor cells expressed cytokeratin ( pan cytokeratin ) but were negative for chromogranin , thus excluding neuroendocrine tumors . histopathology reveals a cellular tumor with sharp circumscription from the surrounding brain parenchyma ( a ) . the tumor cells are disposed in tubular and cribriform patterns ( b - d ) with hyaline ( c ) material within and around the tumor cells ( asterisk , c ) , highlighted by periodic acid  schiff stain ( c , inset ) . focally , bluish myxoid material was seen within the lumen ( d ) ( a : h and e 10 , b - d : h and e 20 , c , inset : periodic acid  schiff 20 ] a detailed evaluation including a chest x - ray , ultrasonography of abdomen , and whole - body single photon emission ct was performed to look for the primary site of the lesion . he showed good clinical improvement and remains recurrence free at 18 months postoperatively [ figure 1d ] . acc , initially called as a  cylindroma  by billroth , is a malignant tumor arising from secretary cells of the minor and major salivary glands , nasopharynx , lacrimal gland , lung , trachea , mammary gland , and skin . it constitutes 810% of all salivary gland tumors , and the frequency of intracranial spread ranges from 4% to 22% . although acc is relatively common , intracranial acc is relatively uncommon . intracranial spread can occur due to perineural growth , direct extension , and hematogenous spread . the first two modes are the most common , with some authors describing 50% incidence of perineural invasion in acc . hematogenous spread is very unusual like the present case , especially in the absence of an unidentifiable primary , with only 13 cases reported in available english literature table 1 . details of the previously reported patients of metastatic adenoid cystic carcinoma with an unknown primary microscopically , accs are characterized by areas of classic cribriform growth pattern , as nests of tumor cells with discrete , rounded ,  punched - out  gland - like spaces filled with either eosinophilic or basophilic material . the three common types of growth patterns are cribriform ( glandular ) , tubular , and solid . among these three , the solid pattern has the worst prognosis ; however , radiotherapy usually prolongs the survival . in primary accs , p53 has shown inconsistent and unreliable expression , but in recurrent tumors , its overexpression has been seen quite often . another marker expressed in acc with or without perineural spread is the brain - derived neurotrophic factor . e - cadherin has been shown to have a reduced expression in progressive forms of acc . clinically , intracranial accs can present with features of raised intracranial pressure , focal neurological deficits , or a combination of both . surgical decompression , to reduce the mass effects and provide a pathological confirmation , is the primary treatment for intracranial accs followed by radiotherapy . tumor site , tumor stage , the presence of perineural invasion , and tumor grade are said to be the prognostic factors for accs . the survival rates at 5 and 10 years are approximately 50% and 20% , respectively . primary intracranial acc is a rare entity , and cell of origin is still unknown .
adenoid cystic carcinoma ( acc ) is an epithelial malignancy comprising approximately 810% of all salivary gland tumors . 
 intracranial acc without a known primary is an extremely rare pathobiological event . 
 only 13 cases have been reported in available literature . 
 we report a case of a rare intracranial acc in a 35-year - old gentleman presenting with features of raised intracranial pressure . 
 patient had a lesion in the right parieto - occipital lobe and underwent gross total decompression . 
 there was no evidence of any primary after a thorough systemic evaluation . in the postoperative period 
 , he showed a good clinical improvement and was recurrence free at follow - up of 18 months . 
 we also discuss and review the existing relevant literature .