His London solicitor, Stephen Pollard, said that surgeons at the Changi General Hospital in Singapore also removed part of Leeson's colon and part of his large intestine, and consider that the operation went well.
Leeson - who is two and a half years into a six and a half year sentence for a pounds 860m futures trading fraud which led to the collapse of Barings Bank - was due to go under the surgeon's knife today, but the operation was brought forward because he was suffering sickness and abdominal pain.
Mr Pollard said that his client was recuperating in hospital, and there were no plans for any of his family to visit him immediately.
The Foreign Office said that Leeson was visited by a member of consular staff from the British High Commission in Singapore yesterday afternoon following his operation, and that the 31-year-old was awake and able to talk.
An FO spokesman said he had no further information on Leeson's condition or on whether he will require further surgery.
He was moved out of Changi Prison to a secure ward at a public hospital last week after developing pains in his stomach.
Since being diagnosed with cancer, he has launched an appeal to be allowed to complete his sentence in a British jail on medical and compassionate grounds, but any move would require the consent of Singapore's President, which could take up to two months.
Following Leeson's diagnosis, his 58-year-old father William revealed that he too was suffering from the disease and was too sick to visit his son in Singapore. He said at the weekend: "We know it is serious, very serious. Nick has got to fight and Nick will fight. He is a lot like his dad and mother in that respect."Reuse content