Abby Lee Miller has a big fight ahead of her, because her recent health struggles are believed to be related to cancer ... TMZ has learned.
A rep for Miller's doctor, Dr. Hooman Melamed, tells us ... her emergency back surgery Tuesday was to alleviate what he thought was an infection in her spine, but after doing some tests -- he now believes she is suffering from Burkitt Lymphoma ... a form of non-Hodgkins lymphoma.
We're told further testing is needed to confirm the cancer, but she should know for sure in the next day or 2. Regardless, Miller's doc says she'll need another spinal surgery, but is resting comfortably after her first operation.
She's scheduled to be released from the halfway house May 25.