BY MELISSA RUGGIERI

Janet Jackson fans heaved a disappointed sigh when she announced on Christmas Eve that impending surgery would cause her to postpone her "Unbreakable" tour.

It’s now being reported that doctors have discovered a tumor on Jackson’s vocal cords and she is undergoing tests for throat cancer.

RadarOnline.com quotes a "source close to the singer" as stating that Jackson's medical condition "has to be taken care of immediately."

A doctor cited in the Radar report notes that should it be cancer of the larynx, “That would abruptly end her ability to ever perform again.”

Jackson performed a sold-out show at Chastain Park Amphitheatre in September , but was forced to postpone shows in October because of vocal stress.

In her Christmas Eve announcement of the tour postponement – which included a March 3 date at Philips Arena – Jackson asked for prayers from fans and ended her website post with “Gon’ b alright.”

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