I first learned about prophylactic mastectomy in 1977 when I was shopping for a plastic surgeon to rebuild the breast that cancer had stolen from me four years earlier.

Of the 22 women I had asked about their breast reconstruction, four had also had their "good" breasts removed along with the cancerous one so the disease would not strike again. All had lost mothers to breast cancer; one had two older sisters living with the disease; another, a sister and two aunts.

A fifth woman had lost both breasts to cancer before she was 30.According to the statistics, the woman's premenopausal cancer in both breasts put her teen-age daughter at a very high risk of developing the disease at an even earlier age. The woman said she planned to encourage her daughter to consider prophylactic surgery to try to beat the grim odds against her.

In the ancient days of 1977, preventive breast amputation was justified only for women like me who had had cancer in one breast and stood a good chance of developing cancer in the remaining breast.

But now, in 1985, the healthy breasts of women are being amputated because they may, someday, develop cancer. On Sept. 23, 1980, The New York Times told readers: "A growing number of women, considered at high risk for developing breast cancer, have elected to have breasts removed before cancer is actually found."

How did this bizarre business start? Basically, it can be traced to four separate events.

The first event was the discovery that cancer-free breasts contained "premalignant" or "precursor" cells that may become cancerous. Pathologists found a host of benign but unusual cells in the breast including cells that were hyperplastic (larger than normal), dysplastic (oddly shaped) and metaplastic (just strange).

And scientists also learned that clusters of real cancer cells occasionally arise but fail to produce breast cancer.

The second event came in 1972, when the American Cancer Society and the National Cancer Institute launched a national program to screen women with mammography (breast X-rays). The goal of the Breast Cancer Detection Demonstration Project (BCDDP) was to find and treat breast cancers before they could be felt -- while they were small and, therefore, curable.

The BCDDP began with much fanfare but few females until the third event occurred: the widely publicized mastectomies of Betty Ford and Happy Rockefeller in 1974. Almost overnight, 280,000 women entered the program. As women with suspicious areas on their mammograms were biopsied, doctors discovered that many of them had breasts full of unusual cells. The pathologists called them "minimal breast cancer." Surgeons decided these were high-risk women who had to be watched carefully.

With lifelike silicone implants available, the logical solution seemed to be prophylactic mastectomies. This became especially attractive when the fourth event occurred: medical insurance companies, under legitimate pressure from doctors and patients, began to pay for plastic surgery associated with breast cancer.

There appears to be a sharp difference of opinion between surgeons who are primarily concerned with cancer and those whose work is mainly reconstruction. Cancer specialists are more reluctant to turn to prophylactic mastectomy unless a woman has many high-risk factors, especially a personal or family history; plastic surgeons are more willing to remove healthy breasts if their owner has three or more risk factors.

Some women, however, do have sharply elevated risks, including those who developed cancer in one breast and have a good chance of growing cancer in the second. Certainly, the four women whose families were riddled with the disease and the fifth woman's young daughter would encounter little medical opposition to prophylactic mastectomy.

But whether they are motivated by terror, vanity or insurance coverage, thousands of women have elected to have healthy breasts cut off because of those four disparate events that converged in the 1970s.

Until the New York Times article appeared, the prophylactic mastectomy controversy simmered on the back burners of medical meetings and journals.

Afterward, however, the subject became a hot national story. In the Dec. 1, 1980, issue of Newsweek carried an interview with a delighted and relieved 44-year-old California woman, Carol Koch, who had had her breasts removed after her mother had developed cancer four years earlier.

"It's so wonderful to get rid of that fear that I had lived with," she explained. In a subsequent article in The Wall Street Journal, Koch compared prophylatic mastectomy to getting the Salk vaccine to prevent polio.

The Breast Cancer Task Force of the National Cancer Institute started to study the issue, but precise data were impossible to acquire. One estimate suggested that 10,000 women had prophylactic mastectomies in 1983.

One study of 1,200 prophylactic mastectomies found microscopic cancer cells in only 9.4 percent of the removed breasts. There is no way to know how many of the microscopic cells would have developed into life-threatening cancer. Last week, a study of 10,366 women concluded that only 4 percent of the women with benign growths had a "medically significant" increase in risk of breast cancer.

"It boils down to needless surgery versus needless loss of life," says Dr. Vincent R. Pennisi, a San Francisco plastic surgeon. " If I do 10 prophylactic mastectomies and nine are needless, it's still worth it to save one life."

But Dr. Marc Lippman, head of the Breast Cancer Section of the National Cancer Institute, disagrees. "I don't think there's a place for prophylactic mastectomy in the general population. I think it's pretty aggressive self-mutilation."

As someone who did have to lose a breast because of real cancer, I think so, too.