A new Irish retrospective study has identified factors associated with breast cancer in 57 women under 40 years old at diagnosis. Breast cancer in young women has been reported to be more aggressive than breast cancer in older women. The women, who were diagnosed or treated between 2001 and 2007, had an average age of 35, with a range of 27 to 39 years. Fifty-one of the women had a palpable lump when first evaluated for breast cancer and 41 had no family history of breast cancer. Mammography was found to be less sensitive than ultrasound in diagnosing the tumors (64.3% versus 82.4%), whereas fine needle aspiration was 92.5% sensitive for malignancy.

Twenty-nine (50.9%) of the women underwent breast-conserving surgery (lumpectomy), of whom seven subsequently had mastectomies due to a lack of clean margins. Twenty-six (45.6%) of the women had a mastectomy as first-line surgical treatment, whereas two of them (3.5%) were treated palliatively due to metastatic disease. The average tumor size was 2.13 cm for those who had lumpectomies and 3.95 cm for those who had mastectomies.

Among the 55 women who had surgery, 47 (85.5%) of the tumors were invasive ductal breast cancer, 31 (57.4%) were grade II, and 22 (40.7%) were grade III. Lymphovascular invasion (invasion of the cancer cells into the blood vessels or lymphatic channels) was found in 28 (50.9%) of these cases, whereas 22 (40.0%) were lymph node positive. Forty-three (76.8%) of the tumors were estrogen receptor positive, 22 (39.3%) were progesterone receptor positive, and 16 (30.2%) were HER2 positive.

Neo-adjuvant chemotherapy was administered to five (9.3%) of the surgically treated patients, and adjuvant chemotherapy was administered to 44 (80.0%) of them. Forty-two (76.4%) of the surgically treated patients received radiotherapy. Forty-two (76.4%) of the patients were treated with tamoxifen, whereas four were treatment with Herceptin. The mean Nottingham prognostic index was 4.37 (range 2.2-8.4), which suggests an intermediate risk of relapse. The Nottingham prognostic index is based on tumor size, tumor grade and lymph node status. Forty-nine (86.0%) of the study participants were alive at an average follow-up period of 52 months and 47 (82.5%) remain free of recurrence. The authors remark that the study reports a low proportion of family history of breast cancer and a high proportion of grade I and grade II hormonally active tumors in the study group. This suggests less aggressive and more hormonally responsive breast cancer than anticipated.