Legislation introduced by Mayor London Breed on Tuesday, Oct. 24, would rename the block of Grove Street between Franklin Street and Van Ness Avenue in honor of Michael Tilson Thomas, who served as music director of the San Francisco Symphony for25 yearsand is now the orchestra’s Music Director Laureate.

The bill, which must be approved by the Board of Supervisors, would designate the block, which passes the entrance of Davies Symphony Hall, as MTT Way, invoking the conductor’s longtime nickname.

“The story of the classical music, arts, and culture scenes in San Francisco is intertwined with the artistic journey of Michael Tilson Thomas,” the mayor said in a written statement.

“Today, we not only recognize him as a vital part of the cultural makeup of the City, we also celebrate the fact that he has been San Francisco’s proud ambassador on the world stage.”

Thomas, 78, was diagnosed two years ago withglioblastoma multiforme, an aggressive form of brain cancer. He returned to the concert stage following surgery and has sustained an active career since.

But last weekend, in performances ofBeethoven’s Ninth Symphonywith the orchestra, he appeared visibly weakened. Breed was present on Saturday, Oct. 21, for the second of the three concerts.

Thomas made his first appearance with the Symphony in 1974, in a program of music by Mahler and Mozart. He was a regular guest with the orchestra through the ensuing years, before taking up the post of music director in 1995.

The quarter century he spent at the orchestra’s helm was uniquely successful, marked by an expansion of the repertoire, artistic excitement and a discography that stands as a legacy of this period in the organization’s history.

“It’s a fitting tribute to MTT’s lasting impact that the block of Grove Street in front of Davies Symphony Hall, where he’s captivated multitudes in thousands of concerts over the years, will now be known as MTT Way,” Symphony CEO Matthew Spivey said in a statement.

In his statement, Thomas responded to the recognition with characteristic ebullience.

“What a tremendous honor, and what fantastic fun,” he said. “I will always treasure that symphony goers will pick up their Davies Symphony Hall tickets, and that Ballet and Opera goers will get their after-performance transportation on ‘MTT Way.’ ”

Reach Joshua Kosman:jkosman@sfchronicle.com