CASE Continued: Imaging findings
Given her age, the patient initially undergoes targeted ultrasonography. The grayscale image (FIGURE 2) demonstrates multiple mildly dilated ducts (white arrows) with surrounding hyperechogenicity of the fat (red arrows), indicating soft tissue edema. No intraductal mass is imaged. Given that the ultrasonography findings are not completely negative and are equivocal for malignancy, bilateral diagnostic mammography (FIGURE 3, left breast only) is performed. Standard full-field craniocaudal (FIGURE 3A) and mediolateral oblique (FIGURE 3B) mammographic views demonstrate a heterogeneously dense breast with a few calcifications in the retroareolar left breast (red ovals). No associated mass or architectural distortions are noted. The mammographic and sonographic findings do not reveal a definitive biopsy target.
Ductography
When a suspicious abnormality is visualized on either mammography or ultrasonography, the standard of care is to perform an image-guided biopsy of the abnormality. When the standard workup is negative or equivocal, the standard of care historically was to perform ductography.
Ductography is an invasive procedure that involves cannulating the suspicious duct with a small catheter and injecting radiopaque dye into the duct under mammographic guidance. While the sensitivity of ductography is higher than that of both mammography and ultrasonography, its specificity is lower than that of either modality.
Most cases of pathologic discharge are spontaneous and are not reproducible on the day of the procedure. If the procedural radiologist cannot visualize the duct that is producing the discharge, the procedure cannot be performed. Although most patients tolerate the procedure well, ductography produces patient discomfort from cannulation of the duct and injection of contrast.
Magnetic resonance imaging
Dynamic contrast-enhanced magnetic resonance imaging (MRI) is the most sensitive imaging study for evaluating pathologic nipple discharge, and it has largely replaced ductography as an adjunct to mammography and ultrasonography. MRI’s sensitivity for detecting breast cancer ranges from 93% to 100%.6 In addition, MRI allows visualization of the entire breast and areas peripheral to the field of view of a standard ductogram or ultrasound scan.9
Clinicians commonly ask, “Why not skip the mammogram and ultrasound scan and go straight to MRI, since it is so much more sensitive?” Breast MRI has several limitations, including relatively low specificity, cost, use of intravenous contrast, and patient discomfort (that is, claustrophobia, prone positioning). MRI should be utilized for pathologic discharge only when the mammogram and/or targeted ultrasound scans are negative or equivocal.
CASE Continued: Additional imaging
A contrast-enhanced MRI of the breasts (FIGURE 4) demonstrates a large area of non-mass enhancement (red oval) in the left breast, which involves most of the upper breast extending from the nipple to the posterior breast tissue; it measures approximately 7.3 x 14 x 9.1 cm in transverse, anteroposterior, and craniocaudal dimensions, respectively. There is no evidence of left pectoralis muscle involvement. An MRI-directed second look left breast ultrasonography (FIGURE 5) is performed, revealing a small irregular mass in the left breast 1 o’clock position, 10 to 11 cm from the nipple (red arrow). This area had not been imaged in the prior ultrasound scan due to its posterior location far from the nipple. Ultrasound-guided core needle biopsy is performed; moderately differentiated invasive ductal carcinoma (IDC) with high-grade DCIS is found.
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