Due to additional cancer detection on a per-patient Imaging of Invasive Breast Cancer level, MRI is considered optional, despite a lack of definitive data supporting classical improved outcomes and continued controversy regarding potential harms. Considering the evidence above, MRI-detected suspicious masses >2 cm from the index malignancy or nonmass enhancement significantly larger than expected from mammographic/sonographic findings should be sampled before using MRI findings to alter surgical planning or change treatment recommendations. MRI Breast Without IV Contrast There is no evidence to support the use of noncontrast breast MRI in evaluating extent of disease. US is the most established noninvasive imaging test for assessing the axilla following a clinically or imaging detected suspicious lymph node. US features associated with a higher likelihood of malignancy include short-axis lymph node size >1 cm, cortical thickness of >0.3 cm, and an absence of a fatty hilum [90-93]. There is a wide range of reported sensitivity and specificity for axillary US, and none of these imaging features are specific enough to avoid the need for histologic sampling. The sensitivity ranges from 26.4% to 94%, and the specificity ranges from 53% to 98% [94-97]. Axillary US alone has a relatively low NPV to rule out metastatic disease [36,98]. A meta-analysis of 21 studies showed that US combined with needle biopsy improved the sensitivity from 61% to 79% [99-101]. US-guided core needle biopsy was superior to US-guided FNA in a meta-analysis of 1,353 patients with newly diagnosed invasive breast carcinoma, with a reported sensitivity of 88% for core biopsy and 74% for FNA [102]. Axillary US and an MRI performed similarly (sensitivity of 99.1% versus 97.4% and specificity 15.4% versus 15.4%, respectively) in evaluating axillary lymph nodes.
Imaging of Invasive Breast Cancer. Due to additional cancer detection on a per-patient Imaging of Invasive Breast Cancer level, MRI is considered optional, despite a lack of definitive data supporting classical improved outcomes and continued controversy regarding potential harms. Considering the evidence above, MRI-detected suspicious masses >2 cm from the index malignancy or nonmass enhancement significantly larger than expected from mammographic/sonographic findings should be sampled before using MRI findings to alter surgical planning or change treatment recommendations. MRI Breast Without IV Contrast There is no evidence to support the use of noncontrast breast MRI in evaluating extent of disease. US is the most established noninvasive imaging test for assessing the axilla following a clinically or imaging detected suspicious lymph node. US features associated with a higher likelihood of malignancy include short-axis lymph node size >1 cm, cortical thickness of >0.3 cm, and an absence of a fatty hilum [90-93]. There is a wide range of reported sensitivity and specificity for axillary US, and none of these imaging features are specific enough to avoid the need for histologic sampling. The sensitivity ranges from 26.4% to 94%, and the specificity ranges from 53% to 98% [94-97]. Axillary US alone has a relatively low NPV to rule out metastatic disease [36,98]. A meta-analysis of 21 studies showed that US combined with needle biopsy improved the sensitivity from 61% to 79% [99-101]. US-guided core needle biopsy was superior to US-guided FNA in a meta-analysis of 1,353 patients with newly diagnosed invasive breast carcinoma, with a reported sensitivity of 88% for core biopsy and 74% for FNA [102]. Axillary US and an MRI performed similarly (sensitivity of 99.1% versus 97.4% and specificity 15.4% versus 15.4%, respectively) in evaluating axillary lymph nodes.