Clinical Imaging 37 (2013) 415–419

Pictorial Essay

Imaging features of breast malignancy: breast ultrasound and MRimaging correlation

Vincenzo Giuliano⁎, Concetta Giuliano

Department of Diagnostic Radiology, Vincon Diagnostic Center, Nova Southeastern University College of Medicine, Winter Springs, FL 32708–5079, USA

Received 16 August 2012; accepted 14 September 2012

Abstract

Recent advances in breast imaging, including volumetric breast ultrasound and breast magnetic resonance (MR) imaging, now providemultiplanar capability for detailed morphologic assessment of breast malignancies. This article describes the imaging findings of commonbreast cancers, utilizing volumetric breast ultrasound with MR imaging correlation. Knowledge of the characteristic appearances of breastmalignancy can facilitate the diagnosis and management of breast masses, particularly when obscured by excessive breast density onmammography examinations.© 2013 Elsevier Inc. All rights reserved.

Keywords: Breast malignancy; Breast imaging; Ultrasound, 3D; MRI

1. Introduction

The evaluation of small breast masses can be problematic indealing with dense breast parenchyma. Breast density is asignificant technical limitation of the sensitivity of conven-tional mammographic screening, which can result in missedcancers or the discovery of later stage cancers inwomen,whichmay require more aggressive treatment options. We havesuccessfully implemented volumetric breast ultrasound(VBUS) and magnetic resonance (MR) imaging in mammo-graphically dense breasts as part of a multimodality approachto dense breast screening. The aim of this pictorial essay is todescribe the imaging features of breast malignancy using thesemodern breast imaging modalities. Another aim is to showhow specific morphologic features can be used to distinguishthe two most common breast malignancies, infiltrating ductalcarcinoma from invasive lobular carcinoma.

The specific morphologic features of breast malignancyon VBUS and breast MR imaging are irregular margins and/

⁎ Corresponding author. Department of Diagnostic Radiology, VinconDiagnostic Center, Nova Southeastern University College of Medicine,5732 Canton Cove, Winter Springs, FL 32708–5079, USA. Tel.: +1 407699 7787; fax: +1 407 699 7963.

E-mail address: giulianomd@att.net (V. Giuliano).

0899-7071/$ – see front matter © 2013 Elsevier Inc. All rights reserved.http://dx.doi.org/10.1016/j.clinimag.2012.09.021

or microlobulation; taller than wide appearance; the “halosign,” an indicator of the angiocentric tumor interface; andthe “thumbprint sign,” a characteristic low signal on T2-weighted MR images, representative of intratumoral fibrosisand desmoplastic change. A comparison between invasiveductal carcinoma (IDC) and invasive lobular carcinoma ofthe breast, the two most common breast malignancies, issubsequently presented.

2. IDC

IDC is the most common malignant breast neoplasmencountered clinically, representing 78% of all breastmalignancies [1]. The most common imaging findings ofIDC on VBUS include a spectrum of solid breast massesranging from irregularly marginated, spiculated, and micro-lobulated masses (Fig. 1) to ovoid, well-circumscribedmasses, which are hypoechoic, hyperechoic, or of mixedechogenicity (Fig. 2). On MR imaging, characteristic earlyenhancement at 90 s with rapid washout is seen onpostcontrast volumetric T1 fat-suppressed scans (Fig. 3).

A unique morphologic feature of IDC is a descriptor wehave termed the halo sign. This finding can be observed inboth breast ultrasound and MR imaging studies and can be

Fig. 1. Classic appearance of an IDC on VBUS is that of an irregularlymarginated, spiculated mass, which is “taller than wide” (top image).A microlobulated hypoechoic mass is another classic feature of IDC(bottom image).

Fig. 2. An ovoid hypoechoic mass with well-circumscribed margins is anatypical feature of IDC (top image). This appearance is indistinguishablefrom fibroadenoma (bottom image). This diagnostic dilemma can generallybe resolved with the use of MR imaging.

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regarded as a unique descriptor of IDC. On ultrasound, this isseen as a distinct hypoechoic ring or collar (Fig. 4). On MRimaging, an enhancing ring or band is seen on volumetric T1fat-suppressed scans (Fig. 5). We have postulated that thehalo sign could represent a reactive “angiocentric” tumorinterface, analogous to the characteristic “bull's eye” lesionof IDC seen on mammography [2].

Another morphologic feature unique to IDC is the presenceof considerable tumor fibrosis. Desmoplasia is a more accuratepathologic descriptor of this phenomenon in tumor specimenofIDC and refers to the presence of a dense collagenous stroma,the so-called “desmoplastic response” of breast malignancy,chiefly responsible for the clinical presentation of a tumor or“lump” in the breast [3]. Several mechanisms have beenproposed that result in myofibroblast activation and collagensynthesis in the interstitium of the breast tumor [4]. On VBUS,tumor fibrosis can be seen as intratumoral hypoechogenity orheterogenous echogenicity with acoustic shadowing (Fig. 6).However, this is not considered the most reliable sign ofmalignancy by ultrasound.

Unlike ultrasound, MR imaging is particularly sensitivein the detection of desmoplasia, with characteristic low

signal intensity on T2-weighted images. We have termed theunique low T2 intratumoral signal as the thumbprint signbecause of its resemblance to a thumbprint (Fig. 7). Thisunique digital signature is often overshadowed by postcon-trast T1 enhancement, the basis of computer assisteddetection methods in conjunction with modern volumetricbreast MR imaging. The presence of desmoplasia, particu-larly in small masses, can be subtle and clinically occult topalpation, mammography, and both VBUS handheldultrasound (HHUS) detection. The multiplanar functionalityof modern VBUS and breast MR imaging techniques alsooffers a theoretical advantage to HHUS in the detection ofsmall IDCs, which can be easily missed in the dense breast orlarge breasted screening population.

3. Invasive lobular carcinoma

Infiltrating lobular carcinoma (ILC) is the second mostcommon breast malignancy, second only to IDC, andaccounts for 10% to 15% of all breast malignancies [5]. Inour experience, there are no classic appearances of ILC,

Fig. 3. IDC shows characteristic peak enhancement on postcontrastvolumetric T1 fat-suppressed scans shown at 90 s The classic appearanceis a spiculated, irregularly marginated mass (top image) but occasionallycan present as a smooth ovoid mass (bottom image), indistinguishablefrom fibroadenoma.

Fig. 5. The halo sign is seen on volumetric T1 fat-suppressed MR imaging asan enhancing ring (arrow), representing tumor neovascularity of IDC. This isa helpful sign in the staging of tumor margins.

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which typically evade mammographic diagnosis and canalso be occult to clinical examination. Diagnostic features ofILC can include subtle thickening in the upper, outer

Fig. 4. The halo sign is a diagnostic feature of IDC, with a distincthypoechoic ring on VBUS (arrow).

quadrant of the breast, with or without breast asymmetry, orarchitectural distortion [6]. Others describe a spiculated orirregularly marginated mass on mammography 44% to 65%of the time and, less likely, as a round or well-circumscribedmass in 1% to 3% of cases [7,8]. In our experience, ILC canelude diagnosis, particularly in the screening dense breastpopulation, on both conventional mammography andHHUS. Some have proposed that this could be due to thelow density of the tumor, which is similar to normal breastparenchyma, and absence of desmoplastic response [9]. Thesensitivity of mammography in the detection of ILC rangesbetween 57% and 81% [10]. However, this does notaccurately reflect dense breasts, in which ILC is frequentlynot seen and probably underreported.

MR imaging findings of ILC are sporadic in the literature.We have found MR imaging to be useful in the diagnosis ofILC, utilizing postcontrast volumetric T1 fat-suppressed

Fig. 6. Desmoplasia associated with IDC is seen on VBUS as acousticshadowing and intratumoral echogenicity (arrow). Due to its subtle nature,this finding is not the most reliable feature of malignancy on ultrasound.

Fig. 7. The classic “thumbprint” sign of desmoplasia related to IDC is thecharacteristic signal loss seen on T2-weighted MR images, which representsintratumoral fibrosis (circle). MR imaging is more reliable than breastultrasound in confirming the presence of desmoplasia.

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imaging, in addition to T2-weighted imaging. In contradis-tinction to IDC, our experience with MR imaging of ILCshows none of the classic or pathognomonic features of

Fig. 8. Comparing and contrasting the enhancement of breast malignanciesat 90 s on postcontrast volumetric T1 fat-suppressed scans show a starkcontrast from the rapid uptake seen with IDC (top image) compared to weak,subtle enhancement of invasive lobular carcinoma (bottom image).

breast malignancy. On postcontrast scans, ILC can resemblea benign appearing mass, with well-marginated and well-circumscribed margins, and weak, delayed enhancement onpostcontrast volumetric T1 fat-suppressed scans (Fig. 8).ILC is best distinguished from IDC during the initial 90-swindow on postcontrast scans. IDC demonstrates a classicpattern of rapid enhancement at 90 s; whereas ILC showsweak or scant enhancement [11]. With ILC, increased signalhyperintensity is also noted on T2-weighted scans (Fig. 9).One key distinguishing feature where MR imaging can beparticularly helpful is the absence of the low T2 signalthumbprint sign of intratumoral fibrotic change, a reliablesign in distinguishing ILC from IDC, even in the presence oftumor enhancement on fat-suppressed volumetric T1 scans.

VBUS can be helpful, particularly in identifying smalltumors, including ILCs, due to a 3-mm slice thickness andhigh pixel resolution on postprocessed volumetric scans[12]. As a result, small ILCs can appear more “malignant” intheir appearance compared to MR imaging based on surfacemorphology, presenting a diagnostic dilemma. VBUS shows

Fig. 9. MR imaging with T2 weighting is more reliable in distinguishingbreast malignancies. Invasive lobular carcinoma shows signal hyperintensityon T2-weighted images (top image) compared to the prominent signalhypointensity associated with IDC on T2-weighted images (bottom image).The signal loss correlates with intratumoral fibrosis to produce thecharacteristic thumbprint sign of IDC.

Fig. 10. Invasive lobular carcinoma presents as a hypoechoic mass withirregular margins, taller than wide appearance, and acoustic shadowing.These tumors are typically less well seen by MR imaging and can evademammographic diagnosis due to the low density of the tumor.

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features of ILC more similar to IDC, typically presenting as ahypoechoic breast mass with irregular margins, “taller-than-wide” appearance, and acoustic shadowing (Fig. 10). In thesecases, MR imaging serves a specific application in theevaluation of ILC to establish the enhancement characteris-tics of the tumor and signal properties on T2-weightedimages in order to distinguish them from IDC. The absenceof a thumbprint sign is felt to be a reliable indicator that thetumor is not IDC.

4. Conclusion

The availability of modern imaging methods hascircumvented the inherent limitations of conventionalmammography, particularly with regard to small breastmalignancies, which can be obscured by excessive breast

density. Knowledge of the characteristic imaging features ofbreast malignancy on VBUS and MR imaging of the breastcan facilitate the diagnosis and management of such cases.

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