A consultant radiologist missed breast cancer in 61 women wrongly given the all-clear, an inquiry has revealed.
Dr Glenn Kelly was making errors in screenings at Accrington Victoria Hospital, in Lancashire, as far back as 2000, the independent report said.
It has highlighted governance and trust failings that could have identified the problems earlier.
But it said women could be confident in the quality of breast screening at East Lancashire Hospitals Trust (ELHT).
The radiologist - the trust's former director of breast screening - has not carried out any clinical work since April 2009 and is currently excluded from duty pending disciplinary proceedings.
Two women affected by the errors spoke of the trauma caused by the misdiagnosis.
"They say to you, you've only got a little bit... get back on with your life - you can't do it," said Glenys Thompson of Barnoldswick.
Her friend Sue Gilmore, also from Barnoldswick, added: "You've got to be able to trust them [the doctors] it is the only way you can sleep at night."
The original blunder came to light through internal monitoring in the screening service which sparked an independent investigation, revealed in September 2009.
Of the 276 cases reviewed between August 2006 and December 2008, 86 women were re-tested and 20 were diagnosed with breast cancer. The trust originally said 18 women had developed cancer.
But additional scrutiny of Dr Kelly's earlier work confirmed that an additional 41 women had suffered a delayed diagnosis of cancer because of incorrect assessments he carried out between 2000 and 2006.
The report, published on Wednesday, said the radiologist had "routinely failed to carry out a full and complete assessment on significant numbers of his patients" going back to 2000.
It found that 92% of his patients had not been assessed in line with national guidelines and none of those called back for reassessment had undergone an ultrasound examination - despite signs of abnormalities on their mammograms.
The report added that the doctor never become proficient in a diagnostic technique called ultrasound guided core biopsy, which national guidelines recommended should be used to screen detected abnormalities.
Dr X - as he is known in the report - insists the missed cancers between 2006 and 2008 were a "direct consequence of illness and stress" which impaired his judgement and concentration, the report said.
Rineke Schram, the trust's medical director, said: "The trust apologises again to all women affected by this incident, and recognises the added distress it has caused to women already suffering the trauma of breast cancer."
Ms Schram said the further 41 women identified during the extended review might have had their breast cancer diagnosed sooner.
"It is important to note that all of these women had been diagnosed with, and received treatment for, breast cancer, long before the initial review was instigated," she added.
"No new cancers have been diagnosed as a result of the extended review."
Report author Frank Burns made a number of recommendations for improvements in breast screening services and processes at the trust, which it said had been followed.