Joseph Anthony "Uncle Joe" Ligambi (born August 9, 1939) is a retired American mobster and former acting boss of the Philadelphia crime family.
 Ligambi is known among law enforcement circles to have a more "old school" approach, in sharp contrast to boss Joseph Merlino's, flamboyant, high-profile style.
 Ligambi is credited by the Philadelphia Police Department's Criminal Intelligence Unit to be "quietly bringing stability back to the troubled Philadelphia-South Jersey branch of the American Mafia" during the 2000s(decade).
 The New York Mafia families have been pleased with Ligambi and his approach, as well as his ability to turn the Philadelphia crime family back into a stable group.
Vincenzo "Vinny" Aloi (born September 22, 1933) is a New York City mobster involved in stock fraud who briefly served as the acting boss of the Colombo crime family.
John "Johnny Boy" D'Amato (died January 1992) was a New Jersey mobster and former acting boss of the DeCavalcante crime family.
 After being recruited by Gambino crime family boss John Gotti to take over the family, he was suspected of engaging in homosexual activity and was murdered in January 1992.
Vincent Louis Gigante ( ; March 29, 1928 – December 19, 2005), also known as "Chin", was a New York Italian-American mobster in the American Mafia who was boss of the Genovese crime family from 1981 to 2005.
 Gigante started out as a professional boxer who fought 25 bouts between 1944 and 1947.
 He then started working as a Mafia enforcer for what was then the Luciano crime family.
 Gigante was one of five brothers: Mario, Pasquale, Ralph and he all became mobsters in the Luciano family, forerunner of the Genovese family.
 Only one brother, Louis, stayed out of the crime family, instead becoming a priest.
 Gigante was the shooter in the failed assassination of longtime Luciano boss Frank Costello in 1957.
 After sharing a prison cell with Costello's rival, Vito Genovese, following Vito's conviction for heroin trafficking, Gigante became a caporegime, overseeing his own crew of Genovese soldiers and associates that operated out of Greenwich Village.
 Gigante was one of Genovese's most loyal supporters, siding with him throughout the struggle for power with Costello.
Giovanni "John the Eagle" Riggi (February 1, 1925 – August 3, 2015) was a New Jersey mobster and member of the DeCavalcante crime family since the 1940s, before the family had acquired its name.
 Riggi was the leader of the "Elizabeth crew" in the family when he was a Caporegime.
 He had been the acting boss during the 1970s and became the official boss around 1980.
 Riggi was incarcerated at the Federal Medical Center (FMC) Devens, Massachusetts on extortion and labor racketeering convictions.
 He was released on November 27, 2012.
Alphonse "Little Al" D'Arco (born July 28, 1932), also known as "The Professor", is a New York mobster who became the acting boss of the Lucchese crime family.
 He was the first boss, acting or otherwise, of a New York crime family to become a government witness.
Vincent John Basciano (pronounced bah-sha-noh) (born November 14, 1959) is an American mobster who became acting boss of the Bonanno crime family after the arrest of boss Joseph Massino.
Ettore "Eddie" Coco (July 12, 1908 Palermo, Sicily – December 1991) was a New York City mobster who served as "acting boss" of the Lucchese crime family in 1967.
Vittorio "Little Vic" Orena (born August 4, 1934) is a New York City mobster who became the temporary acting boss of the Colombo crime family.
 A challenge by Orena to boss Carmine Persico triggered one of the bloodiest Mafia wars of the late 20th century, and the last major mob war in New York to date.
Dominick V. "Quiet Dom" Cirillo (born July 4, 1929 East Harlem) is a high-ranking member of the Genovese crime family, who briefly served as acting boss for the imprisoned Boss Vincent "Chin" Gigante.

Question: Dominick V. "Quiet Dom" Cirillo briefly served as acting boss for a mobster who started out as a what?
Answer: professional boxer