Enlarged lymph nodes were identified when Lester, 22, was tested to determine the cause of back pain that sent him to the disabled list last Monday. The club said Friday he has a treatable form of anaplastic large cell lymphoma, a type of cancer that forms in the body's lymph system.
Manager Terry Francona visited Lester in the hospital Thursday morning and several players commented later that day, before the diagnosis was announced. He also met with the team about an hour before Friday's 2-1 win over the Toronto Blue Jays.
"It was pretty quiet. That's part of our family in here and we're all astonished," reliever Mike Timlin said.
Closer Jonathan Papelbon, who came up through the minors with Lester, said Friday, "they say it's curable or treatable and they're expecting him to be at spring training with us next year."
On Thursday, pitcher Curt Schilling referred to the melanoma his wife dealt with several years ago.
"Having been in a situation where cancer was an operative word, it's an incredibly scary thing," Schilling said. "You're talking about a kid at the beginning of his life."
Lester, a left-hander, is 7-2 with a 4.76 ERA and 60 strikeouts in 81 1/3 innings.
He was called up to the majors for the first time June 10, when he started in a 7-4 loss to Texas. He wasn't involved in the decision. He improved to 5-0 with a 1-0 victory at Kansas City on July 18.
On Saturday, the Red Sox purchased the contract Saturday of
right-handed pitcher Kevin Jarvis from Triple-A Pawtucket and moved
Lester to the 60-day disabled list.
On Thursday, Timlin said baseball pales in significance to Lester's health.
"It's his life. It's not him not being able to get out of the sixth inning," Timlin said. "He's 22. That's a long future not to have if you come up with an illness that you can't get rid of so we are praying for him.
"Winning baseball games, yeah, that's great. Losing baseball games, no, that's not very much fun. But dealing with horrible things in human life, that's a whole lot worse than losing."
Anaplastic large cell lymphoma is one of a group of cancers known as non-Hodgkin lymphoma, said Dr. Robert Soiffer, chief of the division of hematologic malignancies at the Dana-Farber Cancer Institute in Boston.
"It is a disease that can strike at any age," said Soiffer, who is not involved in Lester's treatment. "It's responsive to chemotherapy and very treatable."
Prognosis depends on the stage at which the disease is caught, Soiffer said. Age can also play a limited role in determining a patient's outcome, he said.
"In general, younger patients ... have a better prognosis than older ones," Soiffer said.
Red Sox president Larry Lucchino is a non-Hodgkins lymphoma survivor.
Lester, from Tacoma, Wash., was Boston's first pick in the 2002 draft. In his first four minor-league seasons, he had a 24-22 record with a 3.38 ERA in 73 games, 69 of them starts, and was considered one of the Red Sox's top prospects.
Last year with Double-A Portland he had an 11-6 record and led the Eastern League with a 2.61 ERA.
This season with Triple-A Pawtucket, he was 3-4 with a 2.70 ERA in 11 starts before being promoted.