Catherine S. Giess

Background Parenchymal Enhancement at Breast MR Imaging: Normal Patterns, Diagnostic Challenges, and Potential for False-Positive and False-Negative Interpretation

At magnetic resonance (MR) imaging, both normal and abnormal breast tissue enhances after contrast material administration. The morphology and temporal degree of enhancement of pathologic breast tissue relative to normal breast tissue form the basis of MR imagings diagnostic accuracy in the detection and diagnosis of breast disease. Normal parenchymal enhancement at breast MR imaging is termed background parenchymal enhancement (BPE). BPE may vary in degree and distribution in different patients as well as in the same patient over time. Typically BPE is minimal or mild in overall degree, with a bilateral, symmetric, diffuse distribution and slow early and persistent delayed kinetic features. However, BPE may sometimes be moderate or marked in degree, with an asymmetric or nondiffuse distribution and rapid early and plateau or washout delayed kinetic features. These patterns cause diagnostic difficulty because these features can be seen with malignancy. This article reviews typical and atypical patterns of BPE seen at breast MR imaging. The anatomic and physiologic influences on BPE in women undergoing diagnostic and screening breast MR imaging are reviewed. The potential for false-positive and false-negative interpretations due to BPE are discussed. Radiologists can improve their interpretive accuracy by increasing their understanding of various BPE patterns, influences on BPE, and the potential effects of BPE on MR imaging interpretation.

Qualitative assessment of liver for fatty infiltration on contrast-enhanced CT : Is muscle a better standard of reference than spleen?

PURPOSE Our goal was to determine whether spleen or muscle can be used as a qualitative standard of reference for diagnosing fatty infiltration of liver on contrast-enhanced CT. METHOD Qualitative visual comparisons and quantitative region-of-interest measurements of liver, spleen, and muscle were made on scans of 96 patients who underwent dynamic CT before and after injection of intravenous contrast material. As the standard of reference, the portion of liver assessed was considered fatty if its attenuation measured less than spleen on noncontrast CT. RESULTS In 16 (17%) scans, the portion of liver assessed was fatty on noncontrast CT. After contrast material administration, the attenuation of that portion of liver measured less than splenic attenuation in 93 (97%) of 96 cases (including all 16 fatty livers). Only four (25%) fatty livers, and no nonfatty livers, were visually judged to be less attenuating than muscle after contrast material; these four were the most fatty shown on noncontrast CT. Comparing hepatic and splenic attenuation on postcontrast CT resulted in a specificity of 30% and a positive predictive value of 20%; comparing hepatic and muscle attenuation on postcontrast CT yielded corresponding values of 100 and 100% but a sensitivity of 25%. CONCLUSION For the visual assessment of fatty liver, spleen is not an accurate reference standard on contrast-enhanced CT. However, fatty liver can be diagnosed on contrast-enhanced CT if liver appears less attenuating than muscle-a situation that occurs only if fatty infiltration is pronounced.

Distinguishing breast skin lesions from superficial breast parenchymal lesions: diagnostic criteria, imaging characteristics, and pitfalls.

Superficial lesions are commonly encountered in the breast and may be located in the dermis, hypodermis (subcutaneous fat), or parenchyma. The differential diagnosis varies for each anatomic layer. Dermal lesions that are seen by breast imagers are usually benign skin cysts. Hypodermal lesions, although usually benign, may include lesions that arise from anterior terminal duct lobular units and include papilloma, adenosis, fibroadenoma, and breast cancer. To avoid misclassifying a small superficial breast cancer as a benign dermal lesion, it is necessary to understand superficial breast and skin anatomy and the mammographic, ultrasonographic (U.S.), and magnetic resonance (MR) imaging signs that indicate that a lesion is dermal. Mammography is the optimal modality for localizing calcifications to the dermis or hypodermis. However, U.S. typically has higher resolution for localizing masses than mammography and MR imaging. At US, a lesion may be categorized as dermal (a) if it is contained entirely within the dermis, (b) if a tract that extends from the lesion to the skin is seen, or (c) if a claw of tissue surrounding the margin of the lesion is present. As with other breast lesions, suspicious imaging features should be sought in addition to determining the anatomic origin. If histologic analysis is necessary to characterize lesions with an unknown cause or origin, precautions must be taken to decrease patient morbidity.

Screening Breast MRI in Patients Previously Treated for Breast Cancer: Diagnostic Yield for Cancer and Abnormal Interpretation Rate.

RATIONALE AND OBJECTIVES To determine the cancer detection rate and abnormal interpretation rate of screening breast magnetic resonance imaging (MRI) in previously treated breast cancer patients. MATERIALS AND METHODS Institutional review board-approved retrospective review of the breast MRI database from 2009 to 2011 identified a total of 3297 screening examinations. After excluding genetic mutation carriers, untested first-degree relatives of known mutation carriers, and patients with a history of chest irradiation, there were 1194 (36.2%) examinations in 691 patients previously treated for breast cancer. MRI reports were reviewed to determine MRI findings and breast imaging reporting and data system (BI-RADS) assessments. The longitudinal medical record was reviewed to determine patient demographics and outcomes of imaging surveillance and biopsy. RESULTS Mean patient age at initial cancer diagnosis was 46.1 years, and mean patient age during the study interval was 52 years. Cancer detection rate was 10 per 1000 (1%; 95% confidence interval [CI], 0.5%-1.8%]; 12 of 1194 examinations). Overall 10.7% (128 of 1194) of examinations received an abnormal interpretation, including 5.4% (65 of 1194) BI-RADS 4 or 5 and 5.3% (63 of 1194) BI-RADS 3 assessments with a 9.4% positive predictive value (PPV1; 12 of 128 examinations) and a 17.9% PPV3 (12 malignancies per 67 biopsies). CONCLUSIONS Screening breast MRI in women previously treated for breast cancer detected cancer in 1.0% of examinations, with a 10.7% abnormal interpretation rate, and a PPV for malignancy of 17.9%.

Patterns of Nonmasslike Enhancement at Screening Breast MR Imaging of High-Risk Premenopausal Women

Current U.S. recommendations for breast cancer screening of women with at least a 20%-25% lifetime risk of developing breast cancer include contrast material-enhanced magnetic resonance (MR) imaging of the breasts. The cancer detection rate in high-risk women undergoing screening MR imaging is approximately 10 times higher than that in normal-risk women undergoing screening mammography. Many of these high-risk women commence MR imaging screening while they are premenopausal, when the breasts are most influenced by cyclical hormonal changes. Healthy premenopausal breast tissue enhances in a cyclical and variable manner. This enhancement is described as background enhancement. Typically, enhancement of normal breast tissue occurs in a symmetric and diffuse pattern, and there is little diagnostic difficulty in classifying it as normal background parenchymal enhancement. However, sometimes the pattern is more focal, asymmetric, or regional. It may then be described as nonmasslike enhancement, an observation associated with both benign and malignant breast pathologic conditions. A review of the morphologic features and internal enhancement patterns in normal but nondiffuse background enhancement and abnormal nonmasslike enhancement in high-risk premenopausal women can help improve interpretive specificity and decrease false-positive interpretations. MR imaging pitfalls and interpretation strategies for localized background enhancement and pathologic nonmasslike enhancement in this high-risk population are highlighted. In evaluating nonmasslike enhancement, the use of the Breast Imaging Reporting and Data System (BI-RADS) lexicon to perform careful analysis of morphologic features, along with an understanding of the role and limitations of kinetic information, will help balance early breast cancer detection against false-positive interpretation.

Difficulties and Errors in Diagnosis of Breast Neoplasms

Many perceptual and interpretive factors influence the radiologic detection and assessment of breast neoplasms. Diagnostic problems can be divided into errors of detection and errors of assessment and management. Detection issues may relate to inherent features of the tumor or surrounding tissue, technical problems, or human error. Even when lesions are successfully detected, errors in assessment or management recommendations can cause diagnostic delays. Improper breast imaging-reporting and data system (BI-RADS) usage or failure to integrate mammographic, ultrasonography (US), and magnetic resonance imaging (MRI) findings with clinical findings, all lead to interpretive errors. This article reviews factors affecting the detection and diagnosis of breast cancer, to improve radiologic interpretation, benefit patients by earlier cancer detection, and lessen medicolegal exposure from a missed or delayed cancer diagnosis. Mammography is the primary imaging modality for population-based breast cancer screening, and it is also the usual initial examination performed for diagnostic evaluation of clinical or screen-detected breast abnormalities in women aged 40 years and older. Mammography is supplemented by breast US and/or breast MRI in some cases. This article will, therefore, focus on mammography in reviewing difficulties and errors in cancer diagnosis, with supplemental discussion of breast US and breast MRI.

Risk of Malignancy in Palpable Solid Breast Masses Considered Probably Benign or Low Suspicion Implications for Management

To determine whether solid palpable breast masses with benign sonographic features have less than 2% incidence of malignancy, allowing management by surveillance instead of biopsy.

Interpreting One-View Mammographic Findings: Minimizing Callbacks While Maximizing Cancer Detection

Overlap of breast tissue is a frequent consequence of the necessary positioning and compression of the three-dimensional breast to obtain two-dimensional mammograms. The mammary glands contain fewer anatomically fixed landmarks than solid organs do; thus, variability in positioning can have an even greater effect on mammography than it has on other imaging examinations. Most often, areas of overlapping fibroglandular tissue, also known as summation shadows, are seen on only one of the two standard mammographic views. While striving to detect breast cancer as early as possible, radiologists must learn to visually compensate for apparent abnormalities in the breast that are produced by such tissue overlap. Mammographic interpretation in this setting is made even more challenging by the fact that the only manifestation of breast cancer might be a subtle change on a single mammographic view. Breast cancer might be obscured on one of the two standard views because of the density of surrounding breast tissue, mammographic technique, lesion size or location within the breast, histopathologic characteristics of the tumor, or lack of effect by the tumor on the appearance of surrounding tissues. To heighten awareness of the factors that can lead to either unnecessary recalls or failure to identify breast cancer, cases are reviewed in which false-positive findings and breast cancers were visible on only one mammographic view. Strategies for interpreting screening mammograms and determining which findings merit diagnostic evaluation are outlined so as to help minimize false-positive findings and aid in cancer detection.

Characteristics, Malignancy Rate, and Follow-up of BI-RADS Category 3 Lesions Identified at Breast MR Imaging: Implications for MR Image Interpretation and Management

Purpose To (a) evaluate the frequency of Breast Imaging Reporting and Data System (BI-RADS) category 3 assessment in screening and diagnostic breast magnetic resonance (MR) imaging, (b) review findings considered indicative of BI-RADS category 3, and (c) determine outcomes of BI-RADS category 3 lesions, including upgrades, downgrades, and malignancy rates. Materials and Methods This retrospective study was approved by the institutional review board and compliant with HIPAA. The authors retrospectively reviewed the breast MR imaging database (2009-2011) to identify breast MR images classified as showing BI-RADS category 3 lesions. There were 9216 BI-RADS assessments in 5778 examinations (3360 women). Of the 9216 assessments, 567 (6%) in 483 women (average age, 47.2 years; median age, 47.0 years) were assigned BI-RADS category 3. In women with more than one BI-RADS category 3 lesion, the first lesion reported in the impression was used for data analysis. Outcomes data were available for 435 of the 483 women (90.1%). These women comprised the study cohort. Medical records from January 1, 2009, to May 31, 2015, were reviewed to obtain demographic characteristics and outcomes. χ(2) statistics and 95% exact confidence intervals (CIs) were constructed. Results MR imaging was performed for high-risk screening in 240 of the 435 patients (55.2%) and for diagnostic purposes in 195 (44.8%). Findings included mass (n = 125, 28.7%), focus (n = 111, 25.5%), nonmass enhancement (n = 80, 18.3%), moderate or marked background parenchymal enhancement (BPE) (n = 91, 20.9%), posttreatment changes (n = 16, 3.8%), and other findings (n = 12, 2.8%). Outcomes were as follows: 339 of the 435 patients (78%) did not have evidence of malignancy at more than 24 months, 28 (6.4%) underwent mastectomy (all benign), and 68 (15.6%) had lesion upgrades, with 11 cancers (2.5%). All 11 cancers were diagnosed in women with a genetic mutation or a personal history of breast cancer. No cancer was detected in cases of moderate or marked BPE. Conclusion Six percent of all breast MR imaging assessments were categorized as BI-RADS category 3, with a cancer rate of 2.5% (95% CI: 1.3%, 4.5%). All cancers were in women with a genetic mutation or personal history of breast cancer. Marked BPE does not necessitate a BI-RADS 3 assessment. (©) RSNA, 2016.

Clinical experience with aspiration of breast abscesses based on size and etiology at an academic medical center

Our purpose was to review needle aspiration of breast abscesses and identify factors associated with treatment by aspiration alone versus aspiration with surgical incision and drainage (I/D).