Women with breast cancer detected by screening are having mastectomies that may not be necessary, a surgeon said yesterday.

Women with breast cancer detected by screening are having mastectomies that may not be necessary, a surgeon said yesterday.

Professor Michael Baum, emeritus professor of surgery at University College Hospital, London and a noted critic of the NHS breast screening programme, said women were being deceived about its benefits, which "barely outweighed" the harm it caused.

The £37m scheme screens 1.4 million women a year aged 50 to 64 of whom 7,000 are found to have breast cancer. Some are diagnosed with Ductal Carcinoma in Situ (DCIS), an often benign condition in which cancer cells are present in the lining of the milk ducts but which may not develop into an invasive tumour.

One in every five cases of cancer detected by the screening programme is DCIS and, of those, Professor Baum claimed 40 to 50 per cent were treated by mastectomy, suggesting up to 700 women a year were losing a breast. Yet studies had suggested that three out of four cases of DCIS were benign and would never progress to invasive cancer. Surgeons were nevertheless uncertain how DCIS developed or how best to treat it and felt mastectomies were needed to save lives.

Professor Baum said: "It is one of the false promises of the NHS breast screening programme - come for screening, catch it early and we will save your breast. It is not true.

"I don't think women invited for screening are told the whole truth. They are told some of the truth to encourage them to come for screening, but that is social engineering and I resent that. I really think there is a deception going on."

He added: "One of the reasons I have broken ranks is my deep concern for the penalty many women pay as a result of the diagnosis of DCIS when we are unsure of the clinical history of the disease. We do not know how to treat it and many of these women are inevitably over-treated."

The allegations were denied by the NHS Breast Screening programme. A spokeswoman said: "DCIS can be removed by local excision rather than mastectomy. But between two- thirds and three-quarters of cases of DCIS detected in screening are high grade so there is a very high probability that they will progress to breast cancer."

She said leaflets about the breast screening programme were being revised to include more information on DCIS. "We are proposing to give specific information about the possibility of its being found and some of the uncertainties associated with treatment."

Professor Baum, speaking at the European Breast Cancer Conference in Brussels, said women diagnosed with DCIS were automatically classed as cancer patients even though their disease could be benign.

He told of one young woman he knew who had had problems getting life insurance because her mother had been diagnosed with DCIS, even though she did not have cancer and there was no evidence the condition could be inherited.