▁as ▁traditional ▁gradient ▁cent rif ug ation ▁with ▁F ic oll . ▁A ▁similar ▁method ▁known ▁as ▁I SET ▁Test ▁has ▁been ▁employed ▁to ▁detect ▁circul ating ▁pro state ▁cancer ▁cells ▁and ▁another ▁technique ▁known ▁as ▁Ros ette Step ▁has ▁been ▁used ▁to ▁isol ate ▁C TC s ▁from ▁small - cell ▁lung ▁cancer ▁patients . ▁Similarly , ▁research ers ▁at ▁Massachusetts ▁General ▁Hospital ▁have ▁developed ▁a ▁negative ▁selection ▁method ▁which ▁emp lo ys ▁in ert ial ▁foc using ▁on ▁a ▁micro fl uid ic ▁device . ▁The ▁technique , ▁called ▁C TC - i Ch ip , ▁first ▁removes ▁cells ▁too ▁small ▁to ▁be ▁C TC s , ▁such ▁as ▁red ▁blood ▁cells , ▁and ▁then ▁uses ▁magnetic ▁particles ▁to ▁remove ▁white ▁blood ▁cells . ▁ ▁C TC ▁character ization ▁Some ▁dru gs ▁are ▁particularly ▁effective ▁against ▁can cers ▁which ▁fit ▁certain ▁requirements . ▁For ▁example , ▁Her cept in ▁is ▁very ▁effective ▁in ▁patients ▁who ▁are ▁Her 2 ▁positive , ▁but ▁much ▁less ▁effective ▁in ▁patients ▁who ▁are ▁Her 2 ▁negative . ▁Once ▁the ▁primary ▁tum or ▁is ▁removed , ▁bi ops y ▁of ▁the ▁current ▁state ▁of ▁the ▁cancer ▁through ▁traditional ▁t issue ▁typing ▁is ▁not ▁possible ▁anymore . ▁O ften ▁t issue ▁sections ▁of ▁the ▁primary ▁tum or , ▁removed ▁years ▁prior , ▁are ▁used ▁to ▁do ▁the ▁typing . ▁Further ▁character ization ▁of ▁C TC ▁may ▁help ▁determ ining ▁the ▁current ▁tum or ▁phen ot ype . ▁F IS H ▁ass ays ▁have ▁been ▁performed ▁on ▁C TC