'Dance Moms' star Abby Lee Miller shares selfie from hospital bed: 'How quickly your life can change'

Abby Lee Miller thanked "those who listened" on social media.

"So much gratitude and love for those who listened, those who looked deeper and those who leapt into action," Miller, 51, wrote. "So much more I wish I could say......about how quickly your life can change at the hands of others."

A physician, Dr. Hooman Melamed, told People that Miller had to undergo emergency spinal surgery Tuesday, in which parts of her vertebrae were removed. Doctors later discovered she had non-Hodgkin's lymphoma, according to Melamed.

ABC News reached out to a rep for Miller, but didn't immediately hear back.

The former star was sentenced to a year and a day in prison last year for bankruptcy fraud and bringing $120,000 worth of Australian currency into the country without reporting it.

Before reporting for her sentence last summer, Miller sat down with her former network, Lifetime, for a special titled "Abby Tells All," detailing her deepest fears and coming to terms with her past mistakes.

“I am petrified,” she said during the show. "I hope it won't be as bad as I imagine... If a whole bunch of people want to make your life a living hell, they're going to do it."

She also questioned what would happen when she got out of prison.

"Will I come out and have nothing?" she questioned. "That's more scary than going in."

Dominick Proto contributed to this report.