Fleetwood Mac has announced that long-time bassist John McVie is battling an unspecified form of cancer, and that his treatment will force the group to cancel their upcoming tour plans.

The band was scheduled to begin a 14-date tour of Australia and New Zealand on Nov. 10 in Sydney. While not technically a founding member of the group, McVie joined Fleetwood Mac mere weeks after their formation in 1967 -- in fact, the "Mac" in their name is a shortened version of his last name.

Apart from drummer Mick Fleetwood, McVie is the longest-tenured member of the immensely popular group. To see just how important he is to the band's history and ever-evolving sound, check out this list of the Top 10 Fleetwood Mac John McVie Songs.

The group revealed the news via a post on their official Facebook page. The statement reads in full:

Fleetwood Mac who has just completed the European leg of their phenomenally successful worldwide tour has announced the cancellation of their upcoming 14 date tour of Australia and New Zealand. John McVie, one of the co founding and original members of Fleetwood Mac is now scheduled to be in treatment for cancer during that period of time. "We are sorry to not be able to play these Australian and New Zealand dates. We hope our Australian and New Zealand fans as well as Fleetwood Mac fans everywhere will join us in wishing John and his family all the best.”

We wish Mr. McVie a quick and full recovery.