Berlusconi, 78, was convicted in 2013 of paying for sex with an under-age dancer known as "Ruby the heart stealer" and then abusing his power as premier to cover it up.
The conviction, a seven-year prison term and a lifetime ban from public office were overturned on appeal last year, triggering a counter-appeal by prosecutors to the Court of Cassation.
The court met Tuesday for a hearing that could make or break the media tycoon's aspirations to return to the frontline of Italian politics.
Prosecutor Edoardo Scardaccione told the court such claims deserved contempt.
More From This Section
"The Mubarak's niece episode was worthy of a Mel Brooks film," he said. "The whole world was laughing at us behind our backs."
Scardaccione insisted all charges against the ageing party lover should be reinstated, saying "he had a dragon's passion for minors".
Berlusconi was not present at Tuesday's hearing in Rome, which lasted for three and a half hours before the judges retired to consider a verdict expected by the end of the day.
If the ruling goes against him, a fresh appeal trial will have to take place, an outcome analysts say would further diminish the billionaire's authority over his Forza Italia (FI) party.
"For Berlusconi's immediate future, the outcome is quite crucial," said Giovanni Orsina, an academic at the LUISS business school in Rome and an expert on the media magnate's impact on Italian politics.