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Paper text:
there are many reports of paraganglioma diagnosed on fine needle aspiration cytology ( fnac ) in the literature .
although fnac of a suspected paraganglioma is contraindicated in view of the hypertensive crisis after fine - needle aspiration , this tumor can be an unexpected finding in neck mass fnacs performed in unsuspecting cases .
cytologic features of single cell , loose clusters and occasional acinar configuration of large , oval cells with round to oval nuclei , evenly dispersed chromatin , focally discrete nucleoli , moderate anisocytosis and anisonucleosis have been well described for paragangliomas . in the present case in addition to the acinar and discrete arrangement of cells
, smears also showed few large loose clusters of cells enveloped by thin vascular channels the so called zellballen pattern , a diagnostic feature on histopathology .
we describe a case of a 42-year - old woman presenting with fever on and off since 1 year and neck swelling of 5 months duration .
ultrasonography ( usg ) showed a well - defined heterogeneous highly vascular lesion in right cervical region .
clinical examination revealed a solitary 3 cm  2 cm non - mobile non - tender mass present at the right angle of mandible .
fnac was bloody and pap stained smears revealed cells in clusters , microacinar and rosette like formations as well as singly .
the cells were monomorphic , round to plasmacytoid with round to oval nuclei and a moderate amount of pale granular cytoplasm .
there were in addition , few large loose clusters of cells enveloped by vascular channels on all sides .
these cells showed same cytomorphologic features as surrounding cells [ figure 1a and b ] .
( a ) cells arranged in compact clusters surrounded by vascular channels on all sides ( pap , 100 ) .
( b ) endothelial cells in vascular channel enveloping tumor cells on one surface of the same cluster seen in ( a ) ( pap , 200 ) .
( c ) typical zellballen pattern on histopathology of the same case ( h and e , 100 ) in view of monomorphic cells with the absence of necrosis and mucin , metastatic adenocarcinoma was ruled out .
metastasis of medullary carcinoma of the thyroid was considered on cytomorphology , but was ruled out on the basis of a normal thyroid on usg and absence of specific cytologic features .
histopathological examination confirmed the diagnosis of a benign carotid body paraganglioma [ figure 1c ] .
this case report highlights the presence of loose cell clusters enveloped by thin vascular channels on cytology , a feature which has been occasionally described in anecdotal case reports in intraoperative scrape smears .
the presence of cell clusters with vascular coats on cytology should lead to high index of suspicion for pheochromocytoma / paraganglioma ( adrenal or extra adrenal ) in addition to the usual cytological , clinical and radiological features .
it is important to diagnose this condition pre - operatively in order to avoid any surgical delay .
clusters and discretely scattered cells , with occasional acinar configuration and fine reddish intracytoplasmic granules are the established facts of a paraganglioma .
however cell clusters enveloped by thin vascular channels on cytology the so called zellballen pattern diagnostic of histopathology may be considered as a novel insight and should be sought for in cytology smears when paraganglioma is a high suspicion .
paragangliomas are uncommon tumors arising in paraganglion tissue , which is well represented in the head and neck . 
 a correct pre - operative cytological diagnosis helps in planning early and optimal surgery . 
 cytologic features in carotid body tumor and extra adrenal paragangliomas have been well described and documented . 
 in addition to the acinar and discrete arrangement of cells , smears also showed a few large loose clusters of cells enveloped by thin vascular channels - the so - called zellballen pattern , a diagnostic feature on histopathology . 
 zellballen pattern of paraganglioma on cytology is not a common finding and hence is being reported .