The mass was found during a physical prior to the Pacers finalizing the trade to acquire LeVert. He will undergo further tests.
"On behalf of my family and myself, we want to thank the Indiana Pacers for their support and guidance," LeVert said in a statement. "We are grateful for their extreme thoroughness during the physical process and I am looking forward to joining the team and being part of this great organization as soon as possible."
Pacers president of basketball operations Kevin Pritchard said at a news conference on Saturday that the team is "super confident" LeVert will be able to get back onto the court.
Pritchard noted that as soon as the team found out about the medical issue, "All eyes were trying to help Caris and making sure that we planned this out." Pritchard said the team grew comfortable with the decision to go forward with the trade after receiving feedback from its medical personnel, despite there being no timeline set for LeVert's return.
"But we got comfortable with it, and again, for us, it was looking at in two ways," Pritchard said. "One, how can it help now? And that's what we were hopeful, and it may not be today that he can help us, but we do believe that there's a chance he can help us in the not-so-distant future. And that's what got us comfortable in that there's risk, we're willing to accept that risk, but there's also a human element that I felt like we could jump in there, put our hands on him, trust our community. Modern medicine is incredible."
The Pacers announced they had acquired LeVert and cash considerations from the Brooklyn Nets as part of the four-team trade that sent Victor Oladipo to the Houston Rockets earlier Saturday. The Pacers also received a future second-round draft pick from Houston and a future second-round pick from the Cleveland Cavaliers in the deal.
In a revised version of the trade, Brooklyn sent $2.6 million to the Pacers, as well, sources told ESPN's Adrian Wojnarowski.
The news became official following a Pacers practice in Los Angeles on Saturday. Pacers coach Nate Bjorkgren confirmed that LeVert was away from the team but said he is "excited" to work with him.
"Obviously, I'm very familiar with him. Last year, played against him in the first round of the playoffs, where he was very hard to handle," said Bjorkgren, a former Toronto Raptors assistant. "Very good player and very dynamic, so I've watched a lot of him, coached against him and now looking forward to having him on our Indiana Pacers team."
LeVert, 26, is averaging 18.5 points and six assists in 27.8 minutes per game this season.
ESPN's Eric Woodyard contributed to this report.