A Florida doctor removed a woman’s kidney during back surgery after mistaking it for a cancerous tumor.

Surgeon Ramon Vazquez was assisting then-51-year-old Maureen Pacheco’s anterior spinal fusion when he removed the organ, an administrative complaint revealed.

The general surgeon was working at Wellington Regional Medical Center in Florida when the error occured back in the spring of 2016. The hospital did not immediately respond to Newsweek’s request for comment.

Vazquez noticed a mass when he exposed Pacheco’s pelvic area in preparation for her spinal procedure. Assuming it was a “gynecologic malignancy” or similar, he “clipped, transected and removed [the kidney] in its entirety,” the State of Florida Department of Health’s complaint stated.

A pathologist later confirmed the mass was a pelvic kidney—a normal organ aside from its location.

The complaint called the accidental nephrectomy a “medically unnecessary procedure,” because it was not related to Pacheco’s spine condition. The complaint, filed December 15 2017, could cost Vazquez anything from a fine to his medical license.

Litigation filed on Pacheco’s behalf claimed Vazquez failed to review MRI images clearly showing the pelvic kidney, The Palm Beach Post reported.

“As you can imagine, when someone goes in for a back surgery, she would never expect to wake up and be told when she’s just waking up from anesthesia, that one of her kidney’s has been unnecessarily removed,” Pacheco’s attorney, Donald J Ward, told The Post. A lawsuit was settled in September, the publication reported.

“The case was settled on [Vazquez’s] behalf for a nominal amount due to the uncertainty of litigation and in no way did [he] admit liability by agreeing to this settlement,” the surgeon’s attorney Mark Mittelmark told the Post.

Although most people live a healthy life with just one kidney, long term problems such as high blood pressure and a loss in kidney function may occur, the National Kidney Foundation reports.

Spinal fusions have risen in popularity in the U.S. in recent years. A 2012 analysis published in the journal Spine showed the number of discharges after fusion rose from 174,223 to 413,171 from 1998 to 2008—an increase of 137 percent.

First performed in the 1950s, anterior lumbar interbody fusions became more popular as a treatment for back pain during the 1990s, Spine-Health reported.