"Olli will have surgery to remove the tumour," Dr. Dharmesh Vyas, the Penguins' physician, said in a statement Monday. "Even if it is found to be cancerous, we do not expect that he will need radiation or chemotherapy, and we anticipate a complete recovery.
"In all likelihood, Olli will go on to live a healthy life and this should not affect his ability to play hockey long-term."
Maatta, 20, has been cleared to play until he has the surgery. Vyas said Maatta will likely be able to return to the lineup within four weeks.
"Obviously our first concern is for Olli and his health," Penguins GM Jim Rutherford said. "He is an outstanding young man and has a tremendous future ahead of him.
"The doctors tell us that this is a very treatable condition, and that it can be taken care of with the surgery. The Penguins organization will be there for him and support him every step of the way."
Vyas said the tumour was discovered during pre-season physicals.
Maatta has a goal and four assists in seven games this season.