"It is clearly evident in the response to his passing that he was a truly unselfish and giving person who committed his energy to the kids, programs and the school. He took tremendous pride in our school and never stopped demanding that from others," said Chad Hollwedel, who coaches Centennial's varsity basketball team.

"As a manager, Zach brought that enthusiasm for life — having had cancer in middle school, he had a great appreciation for life every day — to his work," said Mr. Hollwedel. "Having him around was like having another coach on the staff. He took matters into his own hands, and you never had to ask if something was done."

After graduating from Centennial in 2011, he enrolled at the University of Maryland, College Park, where he was studying broadcast journalism and managed the men's basketball team. He had to withdraw from the university in 2012 during his freshman year, when the cancer he had beaten years earlier returned and he faced a second round of surgery.

"He reached out to kids who were cancer patients and encouraged them," his mother said.

He returned to College Park as a part-time student until withdrawing last year because of his illness.

Mr. Lederer was a communicant of the Roman Catholic Church of the Resurrection in Ellicott City.

"He always enjoyed going to Mass and spoke to youth groups at the church about overcoming adversity," his mother said.

"Zach loved life from the time he was a little kid. He gained strength through his struggle with cancer and used to say, 'I'm living the dream,' and he talked frequently about what it was like to be alive," said his maternal grandmother, Elizabeth "Liz" Bobo, a former Howard County executive who is now serving in the House of Delegates.

"And when the cancer came back, he used the opportunity to help other kids with their battle with cancer," said Delegate Bobo, who lives in Columbia. "He lived his life with dignity and was an inspiration until the very end."

"We feel very fortunate that we got another 10 years from the original diagnosis. We feel very blessed," said his mother. "He was the most positive person I've ever known, about everything, not just his illness. He had lots of friends, and his family and friends were very important to him. People naturally gravitated to him."

"Zach was put here for a reason, and that was to help others get through things," said Mr. Senisi.

The Zaching Against Cancer Foundation was founded in honor of Mr. Lederer, who played a major role in the foundation.

"And through the foundation, Zach's spirit will carry on," said Mr. Senisi.

Mr. Lederer enjoyed hiking the Appalachian Trail with his father and sailing with his family, his mother said.

A Mass of Christian burial will be offered at 3 p.m. March 21 at his church, 3155 Paulskirk Drive, Ellicott City.

In addition to his mother and maternal grandmother, Mr. Lederer is survived by his father; a sister, Julia A. Lederer, 18, a freshman at Mount St. Mary's University in Emmitsburg; his paternal grandmother, Sally Lederer of Kent Island; his maternal grandfather, Clifford Bobo of Ellicott City; his maternal step-grandmother, Linda Bobo of Ellicott City; his maternal step-grandfather, Lloyd Knowles of Columbia; and many cousins.

Baltimore Sun reporter Don Markus contributed to this article.