Serie A - AC Milan come back to win thriller
A header from Guillermo Giacomazzi, a Massimo Oddo penalty and a smart Carlos Grossmuller finish had given the home side a three goal advantage at the interval but the introduction of Prince-Boateng at half-time completely changed the complexion of an absorbing encounter.
He fired a fourteen minute hat-trick to draw the sides level before Yepes headed the winner with seven minutes remaining.
An October fixture against Lecce would hardly usually be considered pivotal to the Rossoneri’s hopes of a successful season, but victory at the Via del Mare could prove as important as any this season as Massimiliano Allegri’s side looked to build some momentum following a disappointing start.
Milan's hopes of taking all three points seemed to be cut prematurely short when Giacomazzi got across his man to head the home side into a fourth minute lead from close range following a free-kick from the right.
Milan looked porous at the back but Lecce were profligate in front of goal, with Daniele Corvia missing a particularly presentable chance before further indiscipline at the back cost Milan a second.
Having been left far too exposed by a static defence, Christian Abbiati flapped at a corner before hauling down Coriva to give the hosts the opportunity to double their lead from the spot. Massimo Oddo made no mistake from twelve yards to give his side a deserved two goal advantage.
It was to get worse for Allegri's men before half-time as confusion and indecision in the Rossoneri defence allowed Grossmuller the opportunity to capitalise on a lucky break of the ball to slot past Abbiati, giving Lecce a three-goal advantage with a little under ten minutes of the first half to go.
Milan's limitations at the back were exacerbated by an inability to retain the ball in attack, and the only chance they created of note in the first half fell to Ibrahimovic, who was denied by a fine block.
With such an insipid display, Allegri rung the changes for the second half - and the decision to bring on Prince-Boateng reaped immediate rewards. He fired two blistering efforts on goal before smashing an unstoppable volley past Massimiliano Benassi from a corner to cut the arrears on 49 minutes.
He then repeated the trick a little over five minutes later, this time striking a Cassano square pass first time from outside the box to further cut the deficit.
Milan were a changed team and began a sustained onslaught on a now overworked home defence.
Incredibly Prince-Boateng completed his hat-trick with only 63 minutes on the clock, the Ghanaian following up an Ignazio Abate effort to force the ball over the line and set up a dramatic finish to the match.
With Milan in the ascendancy, Lecce dropped deep to protect the draw and the tactic frustrated the reigning champions for large swathes of the second period but eventually their constant pressure paid dividends when Cassano found Yepes at the back post to secure the three points amid jubilant scenes from the travelling support.