Former Sen. Arlen Specter has been hospitalized with a "serious illness," friends and family of the Pennsylvania lawmaker confirmed to Philly.com on Monday.

According to the Philadelphia Daily News' Dan Gross, sources declined to comment on the nature of the 82-year-old's condition.

In 2005, Specter was diagnosed with Hodgkin's disease. The cancer returned in 2008, but was detected early. Specter returned to the Senate shortly after the cancer went into remission.

Specter, who switched party affiliation from Republican to Democrat in 2009, retired from the Senate after losing his 2010 Democratic primary to Joe Sestak. He served in the Senate for 30 years.

UPDATE 11:20 p.m. ET:

CNN reports that Specter is being treated for a "serious form of cancer" and is fighting for his life, according to a source close to the former senator. According to the source, Specter was diagnosed six weeks ago.

This is a developing story.. Check back for updates..