Former President Joe Biden diagnosed with 'aggressive' prostate cancer

Former President Joe Biden has been diagnosed with prostate cancer, according to a statement from his office released Sunday afternoon.

"Last week, President Joe Biden was seen for a new finding of a prostate nodule after experiencing increasing urinary symptoms. On Friday, he was diagnosed with prostate cancer, characterized by a Gleason score of 9 (Grade Group 5) with metastasis to the bone," the statement read.

"While this represents a more aggressive form of the disease, the cancer appears to be hormone-sensitive which allows for effective management. The President and his family are reviewing treatment options with his physicians," the statement concluded.

A Gleason score of 9 indicates a high-grade, aggressive form of prostate cancer. It further indicates that the cancer cells look very different from normal prostate cells and are likely to grow and spread rapidly.

This places the cancer in the Grade Group 5, the highest-risk category, which is associated with a greater likelihood of metastasis and a more challenging prognosis. Yet despite the cancer’s apparent aggressiveness, its hormone-sensitive nature offers a viable treatment pathway, according to the National Cancer Institute.

Reaction to Biden's diagnosis started to roll in as the news broke.

President Donald Trump said he was "saddened" by Biden's diagnosis.

"Melania and I are saddened to hear about Joe Biden’s recent medical diagnosis. We extend our warmest and best wishes to Jill and the family, and we wish Joe a fast and successful recovery," Trump posted on his Truth Social platform.

Former President Barack Obama posted a sincere message on X on Sunday evening, saying, "Michelle and I are thinking of the entire Biden family. Nobody has done more to find breakthrough treatments for cancer in all its forms than Joe, and I am certain he will fight this challenge with his trademark resolve and grace. We pray for a fast and full recovery."

Former Vice President Kamala Harris posted on X that she and her husband Doug Emhoff were keeping Biden and his family in their prayers.

"Joe is a fighter -- and I know he will face this challenge with the same strength, resilience, and optimism that have always defined his life and leadership," she wrote.

Former Transportation Secretary Pete Buttigieg, who served in Biden's Cabinet, said the former president "is a man of deep faith and extraordinary resilience."

"Chasten and I are keeping him, and the entire Biden family, in our prayers for strength and healing," Buttigieg said in a post on X.

On Tuesday, a spokesperson for Biden confirmed to ABC News that a small nodule was found in the former president’s prostate after "a routine physical exam.”

The discovery of the nodule "necessitated further evaluation," the spokesperson said.

In February 2023, while serving as president, Biden had a lesion removed from his chest that was cancerous. Before entering office, Biden had several non-melanoma skin cancers removed with Mohs surgery.

"As expected, the biopsy confirmed that the small lesion was basal cell carcinoma," White House physician Dr. Kevin O'Connor said at the time. "All cancerous tissue was successfully removed. … No further treatment is required."

Biden’s health had been under scrutiny since before he dropped out of the presidential race in 2024, giving way to then-Vice President Kamala Harris to top the Democratic presidential ticket.

In an appearance on ABC's "The View" earlier this month, both Biden and former first lady Dr. Jill Biden generally pushed back against the slate of new books from reporters claiming that Biden was dealing with cognitive decline at the end of his presidency.

"They are wrong. There's nothing to sustain that," Biden said.

Prostate cancer is the most common cancer and the second-leading cause of cancer death among men in the U.S., according to the National Institutes of Health (NIH).

An estimated 313,780 new cases of prostate cancer will be diagnosed this year, representing 15.4% of all new cancer cases, with an estimated 35,770 deaths from prostate cancer this year, representing 5.8% of all cancer deaths, according to the NIH. The five-year relative survival rate from prostate cancer, meaning the percentage of people alive five years after diagnosis, is roughly 98%, the NIH says.

Prostate cancer in general usually grows very slowly. While finding and treating it before symptoms occur may not improve men's health or help them live longer it is generally a more treatable type of cancer, even when it has spread.

-ABC News' Eric Strauss contributed to this report.