Homicide detectives are investigating following the grim discovery on November 18.
Ms Borucka, originally from Poland, was last seen alive five days earlier.
A painter found her body after neighbours described a “foul odour” coming from the area where the suitcase was stashed.
Her cause of death is yet to be confirmed.
Detectives are trying to track down Lithuanian Petras Zalynas, 50, who they want to speak to urgently in relation to the death.
They believe he might have fled to Germany and are working with European forces to find him.
They today released a picture of him, as well as a first picture of Ms Borucka.
Detective Chief Inspector Wayne Jolley, of the Met’s Specialist Crime Command, said: “It is thankfully very rare for a body to be found in these shocking circumstances. I know it makes the news of Joanna’s death all the more difficult for those who were close to her.
“Our investigation is progressing well. We have identified Petras Zalynas as a person who we need to speak to in order to find out what happened to Joanna. I’m confident there are people out there who may have seen Zalynas or who might know where he is. I would urge them to come forward.
“I would particularly appeal to London’s Lithuanian community. If you know anything about the whereabouts of Petras Zalynas, please get in touch. You will be supported and your information could hold the key to unlocking this investigation.”
No arrests have been made. Anyone with information is urged to call 101 or tweet @MetCC quoting CAD 4319/18DEC or call Crimestoppers, anonymously, on 0800 555 111.