World-renowned Christian apologist Ravi Zacharias announced in a Facebook post Thursday that he has a malignant tumor of the sacrum, a very rare cancer called Sarcoma.

"We wanted to give you an update on my health, as we know so many of you have been praying and we are so grateful. As many of you know, I underwent surgery to repair my back 3 weeks ago today. The surgery was considered a success, and the surgeon felt it was a strong reconstruction. However, since the surgery I have faced very severe pain, so intense in the night, especially, that I have been unable to sleep," Zacharias, 73, wrote in the post.

"While we have assumed this pain was a natural consequence of the surgery, we have learned in the past week that a biopsy taken during the procedure revealed that I have a malignant tumor on my sacrum—a very rare cancer called Sarcoma. Indeed, we now know this is the cause of my extreme pain. In the past few days, we have been meeting with specialists to determine the next course of action. They will wait until I am fully healed from the back surgery, and in 4-5 weeks, will begin treatment to shrink the tumor. I will not plan to resume speaking at least until the summer," he shared.

The apologist - someone who specializes in explaining and defending the Christian faith - went on to explain that the tumor was discovered during his recent surgery.

“We are trusting the Lord in this, and we believe we have already seen evidence of His hand. For example, the tumor did not show up on any previous scans and was only discovered by my surgeon identifying it during surgery," Zacharias noted.

Zacharias also thanked people around the world for their prayers.

"We received literally thousands of messages from people all over the world saying you were praying. I have every belief God directed and prompted my surgeon to his discovery of this tumor. Margie and I and our family are so grateful for your continued prayers for the journey that lies ahead," he wrote.

He also said his ministry was in good hands during his absence.

"Several of our remarkable speaking team members have been able to step in for me as I am off the road during this time of surgery and recovery. Those of you who will have heard any of our team members speak will have been blessed, I am sure. They will continue to step in for me during this extended time off the road. (I'm so blessed to be part of a team of nearly one hundred gifted RZIM apologists and evangelists, who, in any given month, are speaking hundreds of times in front of live audiences across the globe," Zacharias added.

"I am grateful for the love and support of a team and for your friendships. We are trusting the Lord for His purpose. Please do also pray that God will take away this horrific night pain, which is the most difficult part of waiting," he revealed.

"In the meantime, I want to express my heartfelt thanks for supporting the ministry as it goes forward around the world unabated. We need you to continue to stand with us.

Ravi"

As CBN News reported, Zacharias's wife Margie had updated the progress of her husband after spinal surgery was performed on him late last month.

Zacharias, 73, runs an international apologetics organization, RZIM, and is widely sought after for his eloquent answers to life's biggest questions. He's a prolific author, debater and academic.