It is unknown whether the increase in cancer detection confers a mortality benefit given the large increase in false-positive rates, and the possibility of overdiagnosis. All of the published studies are observational studies, and none of the published studies have assessed whether patient outcomes (including morbidity, survival, or mortality) are improved when women are screened with breast MRI. It is likely that MRI screening may lead to overdiagnosis (i.e., the detection of lesions that would remain asymptomatic in the absence of screening).
Therefore the clinical role of MRI in breast imaging for average-risk women is still generally reserved for diagnostic evaluation, including evaluating the integrity of silicone breast implants, assessing palpable masses following surgery or radiation therapy, and detecting mammographically and sonographically occult breast cancer in patients with axillary nodal metastasis and preoperative planning for some patients with known breast cancer. The role of MRI in screening high-risk women or very high-risk women (such as BRCA1/2 carriers) remains uncertain. There is no clear evidence of a mortality benefit among these women, yet the very high burden of breast cancer, and attendant anxiety, has led to MRI screening among these women due to its high sensitivity for cancer detection at the cost of low specificity.
Studies of screening MRI in women of high genetic risk are ongoing.
Scintimammography, using technetium-99m sestamibi or technetium-99m tetrofosmin, scans the axilla and supraclavicular region while simultaneously imaging the breast tissue. In staging women with a known breast cancer, the contralateral arm is injected with the radionuclide, and lateral and anterior projections are imaged with a gamma camera, with both arms raised. The theoretical advantage of this technology is the potential to obtain staging information, but only small clinical series have been described.
Tissue Sampling (Fine-Needle Aspiration, Nipple Aspirate, Ductal Lavage)
Random periareolar fine-needle aspirates were performed in 480 women at high risk for breast cancer, and the women were followed for a median of 45 months. Twenty women developed breast neoplasms (13 invasive and 7 DCIS). Using multiple logistic regression and Cox proportional hazards analysis, a diagnosis of hyperplasia with atypia was found to be associated with the subsequent development of breast cancer.
Nipple aspirate fluid cytology was studied in 2,701 women who were followed for subsequent incidence of breast cancer, with an average of 12.7 years of follow-up. Breast cancer incidence overall was 4.4%, including 11 cases of DCIS and 93 of invasive cancer, and was associated with abnormal nipple aspirate fluid cytology. Whereas the breast neoplasm rate was only 2.6% for 352 women in whom no fluid could be aspirated, it was 5.5% for 327 women with epithelial hyperplasia and 10.3% for 58 women with atypical hyperplasia.