For years, the Rev. Mike Tegeder publicly fought what many considered unbeatable foes: the Catholic Church hierarchy and former Archbishop John Nienstedt. Tegeder was one of the biggest critics of the church's attempts to block gay marriage, a stance that frequently threatened his status as priest at his two Minneapolis churches, St. Frances Cabrini and Gichitwaa Kateri.

Nienstedt is long gone, gay marriage passed overwhelmingly in Minnesota and Tegeder remains a beloved figure in his congregations. But now he is publicly fighting an even bigger opponent.

Last month, Tegeder shared a message with his congregations on the meaning of Ash Wednesday: "Remember that you are dust, and unto dust you shall return." Then he dropped the bomb: "This always has an impact for me but this year even more. On the Tuesday before Ash Wednesday, I got a call from my doctor telling me that a CT scan of me came back showing lung cancer with metastatic growth into my ribs and spine and abdomen. It was a shock."

An updated post expressed some optimism because the type of lung cancer was less aggressive than expected, but on Sunday Tegeder added more bad news: Tests showed a small patch of cancer on the lining of his brain.

Since Tegeder broke the news, his Facebook page has been flooded with prayers, photos of couples he has married and notes from the scores of people who have been helped and inspired by the maverick priest.

Usually an eloquent and talkative interview, this week Tegeder just sounded tired.

"I don't feel too bad," he said. "I'm going to Rochester [Mayo Clinic] next week to see if they can do anything. Doctors told me there's probably not much they can do. You hate to hear something like that."

At 67, Tegeder is a robust man who likes to ride his bike from his home in Richfield to his parish, Gichitwaa Kateri, a church that ministers to American Indians, just off Lake Street in south Minneapolis. So the cancer was a surprise.

"It hit me out of the blue," he said.

"The funny thing is, I still feel fairly healthy," Tegeder said. He said he may try some targeted therapies, "but this is not likely in my case. In some cases treatment is less beneficial than doing nothing."

Ed Flahavan worked alongside Tegeder in the 1980s at another parish, St. Stephen's. He was saddened to hear about Tegeder's cancer.

"My experience working and living with Mike is that he is superbly pastoral and sensitive to people who come in the front door with whatever pain they had," said Flahavan. "Mike is the kind of guy who, if you came and said you needed $25 to rent a truck because you had to move out of your apartment, he would help you move. He wouldn't just give you the $25 and a nice speech."

Tegeder has also been known to pick fights with institutional rigidity wherever he finds it, but particularly inside his own church.

"Mike is the guy who pulls the pin on the grenade and lobs it over the wall," said Flahavan. "He's got a singular heart."

Tegeder was repeatedly threatened with dismissal by Nienstedt during the fight for marriage equality. During investigations into the church's sex abuse scandal, a whistleblower claimed that Nienstedt even considered labeling Tegeder as "disabled" in order to silence him.

"I don't need to prove anything," Tegeder told me in 2012. "If [Nienstedt] wants to throw me out, I'm fine with it."

Then Tegeder showed me his identification card — he had kept his bus driver's license up to date in case he was ever dismissed from the priesthood.

While his crusade for marriage equality has put Tegeder in the news, it's his dedication to people on the margins — drug addicts, the mentally ill — that has put him in people's hearts.

Katharyn Dawson, Tegeder's sister, lived with him for awhile and said 2 a.m. calls for help were not unusual. "He's realistic," she said. "Very compassionate yet very contemporary. It's a unique combination of traits to help people."

Dawson has seen evidence of her brother's work in countless cards coming in to thank him, and more than 1,500 visits on his CaringBridge page.

The day after his diagnosis, Tegeder spoke to parishioners at the Ash Wednesday service. "We are not just dust, but we are stardust," he said. We are on a blessed journey, headed in the same direction, some of us will get there sooner than others. In God's time it is all the same."

jtevlin@startribune.com • 612-673-1702