What’s lymphoma? Understanding Farrell’s diagnosis

Red Sox manager John Farrell said Friday that he had been diagnosed with lymphoma.Jim Davis/Globe Staff

When most people hear the word cancer, they typically think tumor. But lymphoma, the disease that is forcing Red Sox manager John Farrell to take a medical leave, is a cancer of the immune system.

Farrell announced Friday that he has been diagnosed with a “very treatable” Stage 1 lymphoma, and that he will take a medical leave from the team for chemotherapy treatments, starting Tuesday.

While Farrell, 53, did not disclose other details of his diagnosis, a cancer specialist at Boston’s Dana-Farber Cancer Institute, who has not examined the Red Sox manager, said given the facts that were revealed, Farrell probably has B-cell non-Hodgkin lymphoma.

“It is much more common, and he is in the right age group for it,” said Dr. Matthew Davids, an attending physician in Dana-Farber’s lymphoma program.

Non-Hodgkin lymphoma is the fifth-most-common cancer in the United States, and the median age for diagnosis is about 64, Davids said.

The typical treatment for this type of lymphoma is four and a half months of chemotherapy, he said. But Farrell stated his treatment would last nine weeks, which supports the notion that doctors caught the cancer in its earliest form, known as Stage 1. Farrell noted that the lymphoma was discovered during his recent hernia surgery.

A Stage 1 designation for lymphoma means that cancer has been detected in only one lymph node group, compared with Stage 4, which indicates the cancer has spread to other areas of the body.

Davids said that lymphomas detected early can be treated with an abbreviated course of chemotherapy, followed by a few weeks of radiation.

Davids also suspects that Farrell’s lymphoma would be classified as aggressive because doctors are opting to treat first with chemotherapy. Slower-growing cancers, known as indolent, would be first attacked with radiation.

Still, Farrell announced that his prognosis is good, telling reporters that he has a “highly treatable” form of the disease.

While cancer specialists are careful about using the word “cure” when speaking with patients, Davids said Farrell’s case suggests there is ample room for optimism.

“I do use the ‘cure’ word for this type, though I can’t say for his specific case,” Davids said. “This is typically in the order of a 90 percent cure rate, with nine weeks of chemotherapy, followed by radiation.”

The team manager is not the first person in the Red Sox organization to grapple with lymphoma.

Former pitching ace Jon Lester was diagnosed with a treatable form of anaplastic large cell lymphoma in August 2006, came back in time for 2007 spring training, and pitched the series-clinching Game 4 that year for the Red Sox’ World Series victory. In addition, outgoing Sox CEO Larry Lucchino was diagnosed with non-Hodgkin lymphoma in September 1985.

Farrell told reporters that he has every intention of rejoining the team next season in time for spring training. While every patient is different, the typical recovery time following nine weeks of chemotherapy and two to three weeks of radiation is about three months, Davids said.

That would put Farrell on deck in mid-February, right around the time Red Sox pitchers and catchers head south to start training.