Janet Jackson is undergoing tests for throat cancer.
The 49-year-old singer recently revealed she is postponing the first dates of the next leg of her 'Unbreakable World Tour' - which was due to kick off on January 9 - because she has to undergo surgery and it has now been claimed doctors have discovered a tumour on her vocal cords.
A source told RadarOnline.com: "Doctors found a growth on Janet's vocal cords that could be serious.
It's a medical condition that has to be taken care of immediately."
Despite the health scare, Janet is still hoping to be back on the road later this year.
The insider added: "Janet said she knows that with prayers and her will, she'll be back out on the road in the spring or early summer."
A medical expert warned that the 'Together Again' hitmaker - who postponed shows in October to rest her voice - could be left unable to sing if she does have cancer as patients often need to have artificial voice boxes fitted in order to speak.
Dr. Stuart Fischer told the website: "God forbid that this should be cancer of the larynx. That would abruptly end her ability to ever perform again. Singing would be impossible.
"Surgery would be very complex, and followed by months of radiation treatment."
In announcing the postponement of the tour, Janet - who is married to Wissam Al Mana - appealed to her fans for prayers.
She said on her website: "Hey you guys...Happy Holidays to each and every one of you! I need you to know, I learned today, from my doctors that I must have surgery soon.
"It breaks my heart to tell you that I am forced to postpone the 'Unbreakable Tour' until the spring.
"Please pray for me, my family and our entire company during this difficult time...There will be no further comment."