MILAN (Reuters) -Four-times Italian prime minister Silvio Berlusconi has been diagnosed with leukemia, a source close to the matter said on Thursday, confirming a report by the Corriere della Sera daily.

The 86-year-old Berlusconi has been treated in intensive care since Wednesday in a cardiac unit of Milan's San Raffaele hospital, after suffering breathing problems.

"I spoke this morning with Professor Zangrillo (Berlusconi's personal doctor) and he told me that Berlusconi spent a quiet night, his condition is stable," Foreign Minister and Deputy Prime Minister Antonio Tajani told RAI state television.

Berlusconi's Forza Italia party is part of Prime Minister Giorgia Meloni's right-wing coalition, although the former prime minister does not have a role in government.

The billionaire media tycoon, who made his fortune from commercial television, has suffered repeated bouts of ill-health in recent years and came out of the same hospital just last week.

"He's a rock, so he is going to make it this time as well," Berlusconi's younger brother Paolo told reporters on Wednesday evening as he left the hospital.

As well as his enduring influence on Italian politics, Berlusconi's Fininvest family holding group retains control of the MediaForEurope broadcast business.

(Reporting by Reuters newsroom; editing by Alvise Armellini and Conor Humphries)