▁assumed ▁that ▁different ▁morph ological ▁structures ▁of ▁breast ▁tum ors ▁correspond ▁to ▁certain ▁types ▁of ▁invasion . ▁Therefore , ▁al ve olar , ▁trab ec ular , ▁and ▁solid ▁structures ▁that ▁are ▁character ized ▁by ▁the ▁presence ▁of ▁cell - cell ▁contacts ▁may ▁be ▁referred ▁to ▁morph ological ▁manifest ations ▁of ▁collect ive ▁migration , ▁while ▁discrete ▁groups ▁of ▁tum or ▁cells ▁may ▁be ▁referred ▁to ▁manifest ations ▁of ▁individual ▁migration . ▁Interest ingly , ▁the ▁first ▁batch ▁of ▁data ▁obtained ▁in ▁a ▁study ▁of ▁the ▁expression ▁of ▁cell ▁ad hes ion ▁gen es ▁fully ▁confir ms ▁this ▁hypothesis . ▁For ▁example , ▁there ▁was ▁a ▁decrease ▁in ▁the ▁activity ▁of ▁the ▁gen es ▁of ▁cad her ins , ▁which ▁are ▁responsible ▁for ▁cell - cell ▁contacts , ▁in ▁the ▁order : ▁solid ▁– ▁al ve olar ▁and ▁trab ec ular ▁structures ▁– ▁discrete ▁groups ▁of ▁tum or ▁cells . ▁In ▁this ▁case , ▁the ▁number ▁of ▁expressed ▁gen es ▁of ▁integr ins ▁involved ▁in ▁the ▁ad hes ion ▁of ▁tum or ▁cells ▁to ▁the ▁ext rac ell ular ▁matrix ▁was ▁reduced ▁in ▁the ▁order : ▁solid ▁and ▁al ve olar ▁– ▁trab ec ular ▁structures ▁– ▁discrete ▁groups ▁of ▁tum or ▁cells . ▁ ▁Types ▁of ▁invas ive ▁growth ▁in ▁tum or ▁pro gression ▁and ▁ther apy ▁effic acy ▁In vas ive ▁growth ▁and ▁the ▁development ▁of ▁drug ▁resistance ▁are ▁related ▁processes ▁that ▁play ▁the ▁most ▁important ▁role ▁in ▁tum or ▁pro gression : ▁in ▁particular ▁in ▁met ast asis . ▁It