Dr. Gary Marder in Port St. Lucie, Florida has agreed to pay up to $18 million to reimburse the government for Medicare payments on patients who were not ill.

Prosecutors allege that Dr. Marder falsely diagnosed patients with skin cancer and put them through medically unnecessary radiation treatments, pocketing millions from the insurance companies.

Gloria Strumalo from Port St. Lucie was one of his patients.

She went to Dr. Marder's office for a checkup and was diagnosed with skin cancer.

He recommended radiation therapy.

“I went for 20 days of 2 hours,” Strumalo said.

She had no idea that she didn't need radiation therapy since she didn't actually have skin cancer.

“You just take their word," Strumalo said. "You trust your doctors.”

The bills to the insurance company for her unnecessary treatments were stacking up.

Each visit cost between $1,600 and $3,500.

A few weeks later she went back for a checkup and she didn't believe when Dr Marder said she had to undergo more radiation therapy.

Soon she found out she wasn't alone.

She talked to another of Dr. Marder's patients.

“She said: 'You know that doctor wanted to do radiation on me again," Strumalo said.

Strumalo decided against another set of radiation and opted for surgery instead.

The wound got badly infected.

“There was a lot of discomfort and a lot of pain,” Strumalo said.

She went to Dr. Ted Schiff for a second opinion and she wasn't his first patient from Dr. Marder.

“Sometimes we recognize patients just by the sheer number of biopsies done," Schiff said.

"By the number of procedures and the excessive use of radiation therapy done in an improper manner.”

Schiff said over the course of three to five years he had seen numerous of Marder's patients with benign conditions such as freckles or warts, who were told they had skin cancer.

"In all my years in the medical field I've never seen anything like this," Schiff said. "As doctors we take an oath to do no harm."

Schiff alerted the authorities and worked with the FBI to uncover the scale of the scheme and build a case against Dr. Marder.

A whistleblower lawsuit began in 2013 after Schiff noticed a big increase in patients that had undergone unnecessary treatments.

The lawsuit was picked up by the U.S. Attorney's Office.

The settlement brings an end to the civil case against the dermatologist who has practices in Okeechobee and Port St. Lucie.

As part of the agreement, Marder can pay $5.2 million before the due date and avoid having to pay the full $18 million.

He will also have to give the government a vacant lot he owns on Hutchinson Island in Martin County, valued at $650,000.

Although he owns a 12,700-square-foot home, which is valued at $28 million, it can't legally be seized.

As of Thursday, Marder's medical license was still active, despite previous disciplinary actions against him.

The worst part for Strumalo was when she learned that she never actually had skin cancer on her leg and that the radiation treatments and surgeries were all for nothing. “It’s devastating," Strumalo said.