▁( our ▁own ▁un pub lished ▁data ). <0x09> ▁ <0x09> ▁The ▁established ▁relationship ▁between ▁the ▁al ve olar ▁structures , ▁as ▁one ▁of ▁the ▁manifest ations ▁of ▁collect ive ▁migration , ▁and ▁the ▁rate ▁of ▁l ym ph ogen ous ▁and ▁h emat ogen ous ▁met ast asis ▁allows ▁us ▁to ▁put ▁forth ▁the ▁following ▁assumptions . ▁Appar ently , ▁the ▁cell ular ▁elements ▁of ▁the ▁al ve olar ▁structures ▁differ ▁from ▁tum or ▁cells ▁of ▁other ▁structures ▁by ▁a ▁set ▁of ▁bi ological ▁properties ▁determ ining ▁the ▁met ast atic ▁phen ot ype . ▁The ▁clearer ▁relationship ▁between ▁al ve olar ▁structures ▁and ▁l ym ph ogen ous ▁met ast asis ▁in ▁the ▁men op aus al ▁period ▁suggests ▁a ▁certain ▁role ▁of ▁est rog ens , ▁including ▁also ▁their ▁production ▁in ▁situ , ▁in ▁that ▁tum or ▁cells ▁of ▁the ▁al ve olar ▁structures ▁gain ▁the ▁met ast atic ▁phen ot ype ▁through ▁the ▁l ym ph ogen ous ▁path way . <0x09> ▁ <0x09> ▁Therefore , ▁the ▁data ▁currently ▁available ▁on ▁the ▁features ▁of ▁invas ive ▁growth ▁in ▁car cin omas ▁of ▁different ▁local izations ▁and , ▁in ▁particular , ▁in ▁breast ▁cancer ▁present ▁new ▁opportun ities ▁for ▁the ▁investigation ▁of ▁tum or ▁pro gression ▁patterns ▁and ▁the ▁search ▁for ▁additional ▁key ▁parameters ▁of ▁pro gn osis ▁and , ▁possibly , ▁“ control ” ▁of ▁disease ▁pro gression . ▁ ▁In ▁situ ▁versus ▁invas ive ▁By ▁the ▁degree ▁of ▁invasion , ▁a ▁cancer ▁can ▁be ▁class ified ▁as ▁in