, ▁ 1 8 ▁and ▁ 1 9 ▁( ep ith el ial ▁markers ). ▁The ▁sample ▁is ▁then ▁sc anned ▁on ▁an ▁analy zer ▁which ▁takes ▁images ▁of ▁the ▁nuclear , ▁cy to ker atin , ▁and ▁CD 4 5 ▁st ains . ▁ ▁To ▁be ▁considered ▁a ▁C TC ▁a ▁cell ▁must ▁contain ▁a ▁nucle us , ▁be ▁positive ▁for ▁cy top las mic ▁expression ▁of ▁cy to ker atin ▁as ▁well ▁as ▁negative ▁for ▁the ▁expression ▁of ▁CD 4 5 ▁marker , ▁and ▁have ▁a ▁diameter ▁larger ▁than ▁ 5   µ m . ▁If ▁the ▁total ▁number ▁of ▁tum or ▁cells ▁found ▁to ▁meet ▁the ▁criteria ▁c ited ▁above ▁is ▁ 5 ▁or ▁more , ▁a ▁blood ▁sample ▁is ▁positive . ▁In ▁studies ▁done ▁on ▁pro state , ▁breast ▁and ▁colon ▁cancer ▁patients , ▁median ▁surv ival ▁of ▁met ast atic ▁patients ▁with ▁positive ▁samples ▁is ▁about ▁half ▁the ▁median ▁surv ival ▁of ▁met ast atic ▁patients ▁with ▁negative ▁samples . ▁This ▁system ▁is ▁character ized ▁by ▁a ▁recovery ▁capacity ▁of ▁ 9 3 % ▁and ▁a ▁detection ▁limit ▁of ▁one ▁C TC ▁per ▁ 7 . 5 ▁m L ▁of ▁whole ▁blood . ▁For ▁specific ▁cancer ▁types , ▁alternative ▁methods ▁such ▁as ▁I so Fl ux ▁have ▁shown ▁greater ▁sens itivity . ▁ ▁Par sort ix ▁Method ▁ ▁This ▁autom ated ▁method ▁uses ▁size ▁fil tr ation ▁to ▁en rich ▁larger ▁and ▁less ▁compress ible ▁circul ating ▁tum or ▁cells ▁from ▁other ▁blood ▁components . ▁The ▁Par sort