Mr Ford, 45, has a malignant liposarcoma in his abdomen and will begin chemotherapy within 48 hours.
"I'm optimistic about treatment," said Dr Zane Cohen, who is overseeing his care team.
Mr Ford withdrew from his re-election campaign last week after being diagnosed with the abdominal tumour.
The controversial mayor, who admitted to smoking crack cocaine while in office, maintains a strong support base despite calls for him to resign.
He has also been filmed threatening to kill an unspecified person, as well as making lewd comments about oral sex to journalists.
Liposarcoma is a rare cancer of the soft tissue which accounts for only 1% of all cancers,  Dr Cohen said at a news conference at Mount Sinai hospital in Toronto.
Mr Ford has a 12cm by 12cm sized tumour in his abdomen and another smaller 2cm tumour in his left buttock, which are believed to have grown within the last three years.
"It's a rare tumour, a very difficult tumour," said Dr Cohen.
But he also said this type of cancer had proved to be more sensitive to chemotherapy than other tumours.
Mr Ford will begin a three-day course of chemotherapy at Mount Sinai hospital within the next 48 hours, Dr Cohen said.
This will be followed by a break of 18 days, and then another course.
Mr Ford will then be scanned to see how his tumour has reacted to the treatment before doctors decide whether to administer more chemotherapy or follow up with radiotherapy or surgery.
Mr Ford was admitted to hospital last week after months of abdominal pain.
The discovery of a tumour prompted him to withdraw his candidacy from the mayoral election on 27 October.
His brother and political confidant Toronto Councillor Doug Ford has replaced him on the ballot.
At the same time, Rob Ford's name was added to the ballot papers to run for councillor in his old constituency of Ward 2 in Toronto's Etobicoke North area, signalling his desire to remain a political force in the city.
Dr Cohen said on Wednesday that it was "impossible to predict" how chemotherapy was going to affect Mr Ford.
"I think he's a pretty strong person," he said.
The other top contenders in the mayoral race are former NDP MP Olivia Chow and businessman and former leader of the Ontario Progressive Conservative Party John Tory.
Toronto Mayor Rob Ford has been diagnosed with a "fairly aggressive" rare cancer, doctors treating him have said.