A woman was left with a "black and rotting" wound on her left breast after a surgeon performed an unnecessary mastectomy, a court has heard.
Ian Patterson is alleged to have told patient Judith Conduit, who was 47 at the time, that she was suffering from a rare condition called Dercum's disease.
The court was told Mr Paterson had previously carried out a number of procedures on her to remove lumps from both breasts.
The lumps - which she described as uncomfortable rather than excessively painful - turned out to be benign fatty tissue, the court heard.
Mrs Conduit told Nottingham Crown Court: "He (Paterson) said he could not keep removing the lumps because he was removing too much breast tissue and the only way forward would be to have a bilateral mastectomy."
Mr Paterson is alleged to have told her that there was "no known cure" and that she was only the third person he had seen during his career with the condition.
After the mastectomy, in July 2001, Mrs Conduit had to be rushed to another hospital after a blood clot was discovered close to her heart during the procedure - because surgeons did not have the correct implements to remove it.
The court heard she was left with a "black and rotting" wound and had to spend 10 days in Solihull Hospital.
As part of her recovery, she had to visit the hospital 94 times in the 12 months after the operation.
On discovering further lumps in 2008, Mrs Conduit returned to Solihull for it to be removed and was told although the lump was benign that there was breast tissue left.
She said: "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."
Philip Drew, a senior lecturer in general surgery at the University of Hull, said that while some of the operations carried out would appear reasonable, he believed the mastectomy was not.
He told the court: "In my opinion, the mastectomy was too much surgery for what was in effect recurrent fat necrosis."
Mr Drew also said he believed Mrs Conduit's condition had been "mislabelled" as Dercum's disease.
Ian Paterson was formerly employed by Heart of England NHS Trust and also practised at Spire Healthcare.
Jurors have previously heard claims he carried out completely unnecessary operations for "obscure motives" that may have included a desire to "earn extra money".
He is standing trial after denying 20 counts of wounding with intent against nine women and one man relating to procedures he carried out between 1997 and 2011. He denies the charges.
The trial continues.