Diagnosis:
Normal breasts

Findings:
Axial T1 weighted turbo spin echo, axial T2 weighted turbo spin echo with fat saturation, axial T1 turbo field echo dynamic phase with fat saturation (3 post-contrast phases), and axial T1 turbo field echo dynamic subtraction phase with fat saturation (3 post-contrast phases), and axial T1 high resolution cine sequences have been provided.

Right breast:
Normal fibroglandular enhancement is present which demonstrates a progressive upslope in enhancement character on the post-contrast dynamic phases. No area of hypervascular enhancement or washout is present. No axillary lymphadenopathy or mass.

Left breast:
Normal fibroglandular enhancement is present which demonstrates a progressive upslope in enhancement character on the post-contrast dynamic phases. No area of hypervascular enhancement or washout is present. No axillary lymphadenopathy or mass.

Discussion:
This case serves as an example of a normal breast MRI study. The patient in this case chose to have an MRI study of her breasts due to her strong family history of breast cancer. One mammogram had been performed which showed heterogeneously dense breasts with no abnormality. The patient had no palpable abnormalities or symptoms. 50% of all women who have the BRCA gene will develop breast cancer by the age of 50. 80% will develop breast cancer by the age of 70. Mammography has limited effectiveness in women less than 50 years of age. A screening trial will be performed in the near future to assess the suitability of screening breast MR imaging as an alternative to prophylactic mastectomy.

Several issues have yet to be resolved with breast MR imaging and include no defined standard technique, no defined standard reporting technique or interpretation criteria, and variable opinions with regard to what constitutes abnormal enhancement.

Indications for MR imaging of the breast may include local staging, suspicion of multi-centric disease, a palpable mass with no abnormality identified with other imaging modalities, an indeterminate/unreadable mammogram (i.e. very dense breasts), assessing breast implant integrity, high risk screening, and follow-up imaging after tumor resection to differentiate recurrence vs. scar formation vs. residual disease.

A wide array of imaging technique protocols are in use when breast MRI is performed. This range includes different imaging sequences, imaging planes, unilateral vs. bilateral breast imaging, as well as the use of high and low field MR systems. Most of the studies performed at our institution are done with high-field strength (1.5 T) systems with a dedicated breast coil. A high-field strength system affords a higher signal-to-noise ratio. Fat suppression is more effective and contrast is also improved as field strength increases. Most studies include both breasts imaged at the same time. Axial imaging is performed so both breasts are imaged at the same point of enhancement and direct comparisons can be made. Sagittal and coronal images may be included depending on the individual situation, but axial imaging is invariably included. Axial imaging allows accurate subtraction imaging of both breasts as each is imaged simultaneously. Unilateral imaging may be done, but this would require the patient to return at a later time in order to image the opposite breast when the contrast from the original study is no longer present.

Our standard imaging protocol includes axial T1 turbo spin echo pre-contrast, axial T2 turbo spin echo with fat-saturation, unsubtracted and subtracted axial T1 turbo field echo post-contrast with fat saturation using dynamic sequential imaging technique. The dynamic post-contrast intervals are separated by approximately 30 seconds. It is recommended that at least 3 post-contrast dynamic images be obtained. MRI software is available that allows one to generate a curve based on lesion enhancement over time. Otherwise, the radiologist may choose to “eyeball” the lesion and determine the enhancement pattern. At our institution, we typically perform the latter.

Three basic types of enhancement have been described with respect to breast lesions. The first is a steady enhancement, with a persistent increase in signal after the first two minutes and eventual plateau. The second is maximum enhancement within the first two minutes with a plateau in enhancement character. The third is a maximum enhancement within the first two minutes, with washout of enhancement demonstrated as time progresses.

The first described pattern is that of a benign process, which is the type demonstrated in this case. Fibroglandular enhancement is visualized in both breasts with a progression in signal intensity. Uniform enhancement is identified with no focal area of hypervascularity or enhancement washout. The third pattern is most consistent with a malignant process. Our general rule is that a malignant lesion demonstrates 90% of the enhancement within the first 90 seconds of dynamic post-contrast imaging. Washout is then noted as time progresses, which in our experience, may be gradual or rapid.

Lesion enhancement is certainly not the only discriminating factor. Morphological assessment is also important when assessing lesions on breast MRI. This is especially important when the second type of enhancement pattern is demonstrated, as it is somewhat indeterminate in nature. Ill-defined margins, spiculation, ductal enhancement, and peripheral lesion enhancement, are criteria associated with lesion malignancy. One must take into account all of these factors when assessing a lesion.

Benign lesions may demonstrate smooth, non-spiculated borders, no enhancement or steady progressive enhancement such as in this case. Also, the presence of non-enhancing internal septa has been described as associated with lesions of benignity (specifically fibroadenomas).

Examples of these enhancement and morphologic patterns will be illustrated in later cases. Also, approaches to the diagnostic algorithm will be discussed when necessary.

Sources:
Orel SG and Schnall MD. MR Imaging of the Breast for the Detection, Diagnosis, and Staging of Breast Cancer. Radiology 2001; 220: 13-30.

Liberman L, Morris EA, Joo-Young Lee M, et al. Breast Lesions Detected on MR Imaging: Features and Positive Predictive Value. AJR 2002; 179: 171-178.

Kuhl CK, Mielcareck P, Klaschik S, et al. Dynamic breast MR imaging: are signal intensity time course data useful for differential diagnosis of enhancing lesions? Radiology 1999; 211: 101-110