Arizona Democratic Rep. Raúl Grijalva announced on Tuesday that he has sought medical treatment for a “persistent cough” and was subsequently diagnosed with cancer.

“A few weeks ago, I sought medical treatment for a persistent cough which was initially diagnosed as pneumonia. After further testing and imaging, my physician discovered that I have cancer,” he said in a statement.

Grijalva, 76, said “the diagnosis has been difficult to process” and he has begun treatment. He did not specify the type of cancer he is battling.

“I am grateful to my family, friends and doctors for their support, and I am working hard to get healthy and return to business as usual as soon as I am able,” he said in the statement.

Grijalva has served in Congress since 2003 and is the top Democrat on the House Natural Resources Committee.