The husband of a nurse who said she was told by doctors not to worry about a growing lump in her breast during pregnancy won a $651,482 decision yesterday against a prepaid group medical practice for a misdiagnosis of the cancer that eventually led to her death.

In ordering the award, a D.C. Superior Court jury found that doctors employed by the Capital Area Permanente Medical Group had erred when they failed to conduct tests after Mary Stutsman brought the lump to the attention of three of their doctors.

Stutsman, who was 29 and five months pregnant when she discovered the lump, died last May, three years after her cancer was diagnosed. Her daughter Alexis died in January of leukemia, an illness that Judge Eugene Hamilton told the jury was not related to her mother's cancer.

"I think this accomplishes part of what Mary wanted," her husband Jeremy, of Arlington, said outside the courtroom where the jury announced the award, "but part of what she wanted was something for Alexis, and of course Alexis is not here now . . . .

"The irony is that Mary did everything right," he said. "She did things to keep herself healthy. She was consistent about doing her breast examinations, and when she found a lump she brought it to her doctors' attentions. And still all this happened."

The jury of 10 women and two men was shown a videotape of Stutsman, recorded a few months before her death. She described how she pointed out the mass in September 1981 to her doctors after she found a "pea-sized lump" during a monthly self-examination of her breasts. She said she was told then and several times later that lumps were "very common" in pregnant woman and that hers probably was a "plugged milk duct" that would disappear after she began breast-feeding.

It was not until after her daughter was born and the lump encompassed nearly a quarter of her breast, Stutsman said, that she saw a surgeon and a biopsy was conducted. In March 1982, after cancer was discovered in her right breast and surrounding lymph nodes, a mastectomy was performed. A year later the cancer recurred.

A spokeswoman for the medical group said yesterday that its officials did not believe that the trial evidence supported the verdict and the group may appeal.

The Capital Area Permanente Medical Group, part of the Kaiser Permanente Health Care Program that oversees 12 regional health plans and prepaid medical groups across the country, employs 171 physicians who treat members of the prepaid health plans in the Washington and Baltimore areas at 10 medical centers.

Lawyers for the group argued during the two-week trial that Stutsman first told Drs. Fred Mecklenberg and Kurt Rhymers, her two primary physicians during her pregnancy, about the lump after her baby's birth. Attorneys Richard Boone and Harrison Pledger said that none of the medical records during that period included a notation about a lump and that neither doctor could recall Stutsman's mentioning it.

Stutsman, a teacher before becoming a nurse, described to her attorney, Thomas Mains, on the videotape how she had been alternately relieved and "extremely concerned" as her lump increased in size but her doctors told her not to worry.

"I was definitely looking for reassurance . . . , " she said. "I mean, that was the last thing that I wanted to know . . . that I had cancer and that I was carrying a baby."

Stutsman said she finally decided to see a surgeon on the urging of another doctor, who delivered her daughter. Before those results were completed, Stutsman said, she returned to see Mecklenberg and told him about the tests. Stutsman said Mecklenberg said that he was glad that she had not yet undergone a needle biopsy, which, he said, might have interrupted her nursing.

"I said, 'I'm going to be awfully sorry if 10 months from now I find out that I have cancer and all this time I waited just to nurse my baby.' "

According to doctors who testified at the trial, Stutsman could have had an 80 percent to 100 percent chance of recovery had the cancer been detected when the lump was pea-sized.