Angelo Lonardo, who eventually became the underboss of Cleveland, got away with killing a boss before he was even made! Crazy shit. Also crazy that a mob boss was also a practicing doctor by the sound of it.

"In the 1930s, my cousin, John Demarco, and I murdered Dr. Romano, the former boss of Cleveland, because Romano had a role in the death of my father, and we believe that he killed our cousin on the operating table. At the time, I was not a member of the LCN, but Demarco was. As a result of the Romano murder, Demarco was condemned to death by the Commission for killing a boss without okaying it with the Commission. I was excused for my part in the murder, since I was not an LCN member and did not know the rules. Later, I attended a meeting with Al Polizzi, the boss of Cleveland, in Miami, Florida. It turned out that this was a Commission meeting and that Polizzi was defending Demarco's murder of Romano. I did not sit in on the meeting, but afterwards, Polizzi told me that he had "straightened out" Demarco's problem with the Commission."
Copied from: http://mafiahistory.us/maf-invl.html#03