London — 11,000 former breast cancer patients in England are being told to get checked by a doctor after an inquiry found a rogue surgeon performed hundreds of botched or unnecessary operations over 14 years.

In 2017, Ian Patterson was convicted of 17 counts of wounding with intent and three counts of unlawful wounding and sent to prison.

But an independent inquiry into how his activity went unnoticed for so long, the results of which were released on

Tuesday, found a pattern of abuse that affected thousands of patients.

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Patterson would perform unregulated "cleavage-sparing" mastectomies, which did not remove all breast tissue from patients and meant, for some, that their cancer could come back, the inquiry's report said. He would also perform unnecessary surgeries, sometimes operating multiple times on people who needed no medical intervention at all.

In this Feb. 21, 2017 file photo, former breast surgeon Ian Paterson is shown. AP

"The scale of what happened, the length of time this malpractice went on; the terrible legacy for so many families; it is difficult to exaggerate the damage done, including to trust in medical organisations," the chairman of the inquiry, Rt Rev Graham James, said, according to the BBC.

"Some could have known, while others should have known, and a few must have known," the report released by the inquiry said.

"An absolute monster"

As part of the inquiry, investigators spoke to hundreds of Paterson's former patients. Many of them said they were pressured into surgeries they didn't need and described how they suffered medical problems as a result.

Judith Conduit, who spoke to CBS News partner network BBC News, said Paterson performed 23 unnecessary surgeries on her, which left her with a blood clot near her heart and a rotting wound.

At one point, "he told me I would have to have a bilateral mastectomy," she told the BBC.

"Because I had so many surgeries already I agreed, reluctantly in a way, because I didn't really want it done, but I knew I couldn't keep putting my body through all these general anesthetics."

Years later, she found a benign lump and had it treated by a different doctor. She said, in the course of that treatment, she found out there was still breast tissue left from her mastectomy with Paterson, which wasn't expected.

"I believed for 10 years I had no breast tissue left because I was assured Ian Paterson had removed it all and I would never get breast cancer," she said in testimony during Paterson's trial.

Paterson told another patient, Lesley Cuthbert, that she had cancer in her milk ducts and operated on both her breasts, according to the BBC. After numerous consultations, he told her he had cured her.

"I was so in awe of this man who'd taken this nasty stuff out of my body," Cuthbert told BBC News.

When stories first came out about Paterson's abuse, Cuthbert defended him, saying he had saved her life.

"Shortly afterwards I got that recall letter and was told I'd never had cancer… He's a monster, the man is an absolute monster," she told the BBC.

"I was left with only 50% of my breast to remove a lump that was less than 2cm," another former patient, Debbie Douglas, told Britain's Guardian newspaper.

"I was cut from hip to hip, I had my belly button removed, I had unnecessary chemotherapy — it's left me completely scarred," she said.

Possible manslaughter

The breast cancer deaths of 23 randomly selected former patients of Ian Paterson are now being reviewed, and some relatives of his patients are calling for manslaughter charges.

"The preliminary investigation is to identify whether there is any evidence that gives reason to suspect that any of the former patients of Mr Paterson have died an unnatural death as a result of his potentially substandard treatment," the coroners of Birmingham and Solihull said in a statement.

Currently, the coroners are trying to get in touch with the families of the selected patients. Five other medical professionals have been referred to regulators for possible disciplinary action.

"We need to look at manslaughter charges," Kashmir Uppal, who is representing some of Paterson's patients, told the BBC. "These cases will probably relate to women who actually had breast cancer which came back [following cleavage sparing surgery]. Causation will still need to be established and then we need to look at corporate manslaughter. It takes charges like this before things really change."

The inquiry's report says that a number of reforms — improvements in communication, reporting, and regulation across departments — need to be made to both public and private healthcare organizations in the U.K. to prevent something like this from happening again.

"This report is not simply a story about a rogue surgeon. It would be tragic enough if that was the case, given the thousands of people whom Ian Paterson treated," the chairman of the inquiry, Rt Rev Graham James, said. "But it is far worse. It is the story of a healthcare system which proved itself dysfunctional at almost every level when it came to keeping patients safe."