President Trump Reacts To Joe Biden Cancer Diagnosis

President Trump is breaking from tradition ... because he's got some kind words for Joe Biden.

Trump just reacted to Biden announcing he is fighting cancer ... and Trump's actually being nice to his political nemesis for a change.

POTUS hopped on his Truth Social platform Sunday and posted, "Melania and I are saddened to hear about Joe Biden's recent medical diagnosis."

The Prez adds ... "We extend our warmest and best wishes to Jill and the family, and we wish Joe a fast and successful recovery."

As we reported ... Biden announced Sunday he's fighting an "aggressive form" of prostate cancer that has already spread to his bones.

Trump made it a point to attack Biden on the campaign trail last year and in 2020 ... often taking shots at his age, health and mental capacity ... but he's being pretty graceful and presidential here.

Biden's former Vice President, Kamala Harris, also reacted to the diagnosis ... saying, "Doug and I are saddened to learn of President Biden’s prostate cancer diagnosis. We are keeping him, Dr. Biden, and their entire family in our hearts and prayers during this time."

Harris adds ... "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. We are hopeful for a full and speedy recovery."