Flat Epithelial Atypia of the Breast: Pathological-Radiological Correlation

740 AJR:197, September 2011

definition, the World Health Organization introduced the term “flat epithelial atypia,” which is considered as a descriptive term rather than a specific pathologic diagnosis, and it is defined as a presumably neoplas-tic intraductal alteration characterized by replacement of native epithelial cells by a single or three to five layers of monotonous atypical cuboidal to columnar cells with api-cal snouts [1, 4]. Flat epithelial atypia is dis-tinguished from columnar cell change and columnar cell hyperplasia by the presence of mild cytologic atypia and from atypical duc-tal hyperplasia (ADH) and ductal carcinoma in situ (DCIS) by the absence of architectur-al atypia [1, 5, 6].

There is scant information in the literature on the radiologic features associated with this

Flat Epithelial Atypia of the Breast: Pathological-Radiological Correlation

Silma Solorzano1

Benoît MesurolleAttila OmerogluMona El KhouryEllen KaoAnn AldisSarkis Meterissian

Solorzano S, Mesurolle B, Omeroglu A, et al.

1All authors: Cedar Breast Clinic, Department of Radiology, McGill University Health Center, Royal Victoria Hospital, 687 Pine Ave W, Montreal, PQ, H3H 1A1, Canada. Address correspondence to B. Mesurolle ([email protected]).

Women’s Imaging • Or ig ina l Research

AJR 2011; 197:740–746

0361–803X/11/1973–740

© American Roentgen Ray Society

Percutaneous imaging-guided core- needle biopsy is increasingly be-ing used as an alternative to exci-sional biopsy to assess suspicious

breast lesions. As a consequence, breast radi-ologists are encountering with increased fre-quency lesions designated as “flat epithelial atypia,” a term introduced in 2003 by the World Health Organization Working Group on the Pathology and Genetics of Tumors of the Breast [1].

Flat epithelial atypia is not a new entity. It was described in 1979 as a distinctive in-traepithelial neoplastic breast lesion, which was designated “clinging carcinoma in situ.” Since then, it has been described with a wide variety of labels [2, 3]. Given the lack of a unified nomenclature and clear pathologic

Keywords: breast biopsy, breast cancer, breast ultrasound, flat epithelial atypia, mammogram

DOI:10.2214/AJR.10.5265

Received July 2, 2010; accepted after revision March 2, 2011.

W O M E N ’ SI M A G I N G

OBJECTIVE. This study was undertaken to determine the prevalence of flat epithelial atypia at ultrasound-guided and stereotactically guided needle biopsies, to describe the mam-mographic and sonographic features of flat epithelial atypia, and to determine the signifi-cance of lesions diagnosed as flat epithelial atypia at imaging-guided needle biopsies.

MATERIALS AND METHODS. Retrospective review of a database of 1369 consecu-tive sonographically and stereotactically guided needle biopsies performed during a 12-month period yielded 33 lesions with flat epithelial atypia as the most severe pathologic entity (32 patients). Two radiologists retrospectively reviewed the imaging presentation, by combined consensus, according to the BI-RADS lexicon.

RESULTS. Twenty-two of 33 flat epithelial atypia diagnoses (67%) were obtained un-der stereotactic guidance, and 11 (33%) were obtained under sonographic guidance. Six pa-tients had synchronous breast cancer. Flat epithelial atypia lesions presented mammographi-cally most often as microcalcifications (20/33 [61%]) distributed in a cluster (14/20 [70%]) with amorphous morphology (13/20 [65%]). Sonographically, flat epithelial atypia lesions appeared most often as masses (9/11 [82%]), with an irregular shape (6/9 [67%]), microlobu-lated margins (5/9 [56%]), and hypoechoic or complex echotexture (7/9 [78%]). Twenty-eight of 33 lesions (85%) were surgically excised, confirming the flat epithelial atypia diagnosis in 11 of the 28 lesions (39%), yielding carcinoma in four (14%) and atypical ductal hyperplasia in six (21%). Columnar cell changes without atypia were diagnosed in four lesions (14%), and lobular carcinoma in situ was diagnosed in three lesions (11%).

CONCLUSION. Mammographic and sonographic presentation of flat epithelial atypia is not specific (clustered amorphous microcalcifications and irregular, hypoechoic or com-plex masses). Given the underestimation rate of malignancy, surgical excision should be con-sidered when imaging-guided biopsy yields flat epithelial atypia.

Solorzano et al.Pathological-Radiological Correlation of Breast Flat Epithelial Atypia

Women’s ImagingOriginal Research

AJR:197, September 2011 741

Pathological-Radiological Correlation of Breast Flat Epithelial Atypia

entity. In addition, unlike other entities such as ADH or lobular carcinoma in situ [7], there are limited data concerning the importance of flat epithelial atypia diagnosis at imaging-guided needle biopsies. This study was undertaken to determine the frequency of diagnosis of flat ep-ithelial atypia at ultrasound-guided and stereo-tactically guided needle biopsy, to describe the mammographic and sonographic features of flat epithelial atypia, and to determine the sig-nificance of lesions diagnosed as flat epithelial atypia at imaging-guided needle biopsies.

Materials and MethodsFor this retrospective analysis, approval by the

institutional review board was not required. Per-mission was obtained from the hospital to review the patients’ medical records.

Study PopulationWe reviewed our database of all sonographically

(n = 1136) and stereotactically guided needle (n = 233) breast biopsy procedures performed between January 2008 and January 2009 (one institution).

Clinical and patient data were collected from the electronic medical record system. The pa-tients’ age, personal history of breast cancer, clin-ical presentation (if the lesion was palpable), type of biopsy, number of lesions, lesion size, imag-ing follow-up, and histopathology results were re-corded. Two histopathology results were collected for each lesion: the diagnosis at imaging-guided breast biopsy and the diagnosis at surgical exci-sional biopsy, if available.

Mammographic TechniqueMammography in two standard imaging planes

(mediolateral oblique and craniocaudal) was per-formed using dedicated film-screen mammo-graphic equipment (LoRad M-IV mammographic unit, Hologic). Additional mammographic projec-tions were performed as needed.

Ultrasound Indications and TechniqueBreast sonography was performed using one of

two high-resolution scanners with high-frequency linear-array 10–14-MHz transducers (15L8w broad-band transducer, Sequoia, Siemens Healthcare; high-frequency matrix transducer PLT1204AX, Aplio, Toshiba Medical Systems) to evaluate specif-ic clinical or mammographic abnormalities or as an adjunct to screening mammography in women with dense breasts (mammographic parenchymal density types 3 and 4). The examinations were initially per-formed by sonographers and were reviewed by the radiologists who rescanned the patient. All studies were stored on our PACS (IntelePACS, version 3.7.1, Intelerad Medical Systems).

Core-Needle Biopsy Technique MethodDuring the time period of this study, 1369 con-

secutive needle biopsies were performed under ste-reotactic guidance (n = 233; 11-gauge directional vacuum-assisted breast biopsy procedures [Mam-motome, Ethicon Endo-Surgery] and 9-gauge di-rectional vacuum-assisted breast biopsy procedures [ATEC, Suros Surgical Systems] on a digital ste-reotactic table [LoRad DSM, Hologic]) or sono-graphic guidance (n = 1136; 14-gauge spring-loaded core-biopsy needle [Magnum, Bard Urologic]) on indeterminate breast lesions. Specimen radiographs were routinely obtained for lesions presenting as microcalcifications. All diagnostic breast biopsies were needle biopsies, and no diagnostic breast biop-sies were performed by surgical excision. In our prac-tice, we do not routinely perform a regular mammo-gram (craniocaudal and true lateral view) after each stereotactically guided biopsy. We think that such views could increase clip displacement. We do per-form these views (not the day of the stereotactically guided biopsy) if the patient is to undergo surgery.

Inclusion CriteriaLesions were included in the study if the imag-

ing-guided needle biopsy yielded pure flat epithe-lial atypia as the most advanced lesion at patho-logic examination. Those lesions associated with concomitant lobular neoplasia, ADH, or malig-nancy were excluded. Histologic results of core biopsy and surgical excision were compared when performed. All cases were interpreted by a single breast pathologist. Flat epithelial atypia underes-timates were defined as lesions yielding pure flat epithelial atypia at percutaneous needle biopsy and carcinoma at surgery.

Management ProtocolAll the cases were submitted to a multidisci-

plinary evaluation including assessment of radiolog-ic-pathologic concordance and percentage of lesion removal in correlation with the patients’ history. Factors favoring surgical excision included history of synchronous or previous breast cancer, comorbid factors (e.g., before transplantation), and partial ex-cision of the lesion during needle biopsies. Patients not continuing to surgical excision were recom-mended to undergo a 6-month and then a minimum 1-year mammographic or sonographic follow-up. In our dataset, a more optimal minimum 3-year follow-up period could not be achieved.

Imaging ReviewMammographic and sonographic characteris-

tics were reviewed in consensus by two radiologists with 16 and 4 years of experience in breast imaging. Breast parenchymal density was classified according to the American College of Radiology BI-RADS.

The mammographic and sonographic characteristics were evaluated according to the mammography and ultrasound BI-RADS categories [8]. For vacuum-as-sisted biopsy of microcalcifications, the percentage of lesion removal was evaluated on stereotactic im-ages obtained immediately after biopsy as complete (100% of calcifications removed) or incomplete (re-sidual calcifications present).

Data were entered in a spreadsheet program (Ex-cel, Microsoft). Descriptive analysis was performed.

ResultsOf the 1369 lesions (1164 patients) un-

dergoing imaging-guided needle biopsy, the pathologic analysis yielded malignant results in 382 lesions (28%) and nonmalignant re-sults (including benign and high risk lesions) in 987 lesions (72%). In 32 patients with 33 lesions, percutaneous needle biopsy yielded flat epithelial atypia (33/1369 [2.4%]). Twen-ty-two of 33 flat epithelial atypia diagnoses (67%) were obtained under stereotactic guid-ance, and 11 (33%) were obtained under so-nographic guidance. During the study period, the prevalence of flat epithelial atypia was 9% (22/233) of the stereotactically guided biop-sies and 1% (11/1136) of the sonographically guided biopsies. Subsequent surgical excision was performed in 27 patients with 28 lesions.

Clinical FindingsThe average patient age was 54 years

(range, 38–71 years); two patients were younger than 40 years. Flat epithelial atypia was found during the staging of a synchro-nous breast cancer in six patients. One pa-tient had a history of previous breast carci-noma. One patient was investigated before renal transplantation. None of the flat epithe-lial atypia lesions was palpable.

Imaging FindingsAll 32 patients underwent a mammogram,

and 21 patients an ultrasound as well.

MammographyMammographic breast composition dis-

played a type 4 pattern (extremely dense) in two of 32 patients (6%), a type 3 pattern (het-erogeneously dense) in 17 patients (53%), a type 2 pattern (scattered fibroglandular den-sities) in 11 patients (34%), and a type 1 pat-tern (fatty) in two patients (6%).

On mammography, 27 flat epithelial atypia lesions were visible, and six flat epithelial atyp-ia lesions were occult. Flat epithelial atypia ap-peared as microcalcifications in 20 of the 33 le-sions (61%) (Figs. 1–3), as a mass associated


Solorzano et al.

with microcalcifications in one lesion (3%), as masses without calcifications in four lesions (12%) (Fig. 4), and as distortions in two lesions (6%). The median size of the 27 lesions seen mammographically was 1 cm (range, 0.3–4.0 cm); 56% (15/27) measured 5 mm or less. Table 1 summarizes the features of micro-calcifications (Figs. 1–3). The most common morphologic feature was amorphous (13/20 [65%]), and the most common distribution was clustered (14/20 [70%]) (Figs. 2 and 3).

SonographySonography was performed in 21 patients.

In 11 patients, no significant abnormality was detected at sonographic examination. Ten pa-tients showed evidence of 11 lesions: nine masses in eight patients (9/11 [82%]) and an architectural distortion in two patients (2/11 [18%]). Among these, the two distortions and three masses had a mammographic correla-

tion, whereas the remaining six masses were mammographically occult in a breast with type 3 density. The sonographic features of masses are presented in Table 2. Most masses displayed an irregular shape (6/9 [67%]) with microlobulated margins (5/9 [56%]) and hy-poechoic or complex echotexture (7/9 [78%]) (Fig. 4). The median size of the 11 lesions was 0.8 cm (range, 0.3–1.7 cm). Only 27% (3/11) of the lesions showed increased vascu-larity on Doppler interrogation.

Imaging-Guided Needle BiopsyOf the 33 lesions biopsied, 22 (67%) were

visible on mammogram only (biopsied un-der stereotactic guidance), five (three mass-es and two distortions; 15%) were seen on mammogram and ultrasound (biopsied un-der ultrasound guidance), and six (masses;

18%) were visible under ultrasound only (bi-opsied under ultrasound guidance).

With respect to stereotactically guided vac-uum-assisted biopsy of microcalcifications, complete removal was achieved in 40% (8/20) and incomplete removal was achieved in 60% (12/20) of lesions. All specimen ra-diographs confirmed microcalcification re-trieval (Figs. 2 and 3).

Assessment After Imaging-Guided BiopsySurgical excision—Twenty-seven of 32

patients (84%) underwent surgical excision (28/33 lesions [85%]). Surgical pathology confirmed the diagnosis of flat epithelial atyp-

Fig. 1—49-year-old asymptomatic woman. Screening mammogram detected fine pleomorphic microcalcifications in segmental distribution (not shown). Stereo radiograph taken during biopsy shows fine pleomorphic microcalcifications (arrows). Stereotactically guided biopsy was performed with 9-gauge vacuum-assisted device and yielded flat epithelial atypia (calcifications incompletely removed). Surgical excision pathology found ductal carcinoma in situ.

Fig. 2—48-year-old asymptomatic woman. A, Screening mammogram detected 10-mm cluster of amorphous microcalcifications (arrows). Stereotactically guided biopsy was performed with 9-gauge vacuum-assisted device and yielded flat epithelial atypia (microcalcifications completely removed). B, Specimen radiograph taken during biopsy shows microcalcifications (arrows). Surgical excision pathology revealed atypical ductal hyperplasia.

A

B

A

Fig. 3—47-year-old asymptomatic woman. Screening mammogram performed before renal transplant detected amorphous microcalcifications extending to 5 mm in linear distribution (not shown). A, Spot magnification view shows amorphous microcalcifications (arrows) in linear distribution. Stereotactically guided biopsy was performed with 9-gauge vacuum-assisted device and yielded flat epithelial atypia (microcalcifications completely removed). B, Specimen radiograph taken during biopsy shows microcalcifications (arrows). Surgical excision pathology revealed atypical ductal hyperplasia.

B



ia in 11 of 28 lesions (39%). Columnar cell changes with no atypia were diagnosed in four lesions (14%). Lobular carcinoma in situ was diagnosed in three lesions (11%), ADH was diagnosed in six lesions (21%), and DCIS was diagnosed in four lesions (14%). One DCIS le-sion was associated with a focus of infiltrating ductal carcinoma (IDC) (Fig. 4). Considering that four lesions were upgraded to cancer, the underestimation rate was 14% (four lesions) (Figs. 1 and 4). Two of the four carcinomas had flat epithelial atypia diagnosed at ultra-sound-guided needle biopsy, and two had flat epithelial atypia diagnosed at stereotactically guided needle biopsy.

With respect to the two patients with flat epithelial atypia presenting as a distortion, both underwent surgical excision. In one patient, flat epithelial atypia was confirmed after excision with no sclerosing features to suggest a radial scar, whereas the final pathologic analysis of the second one yield-ed ADH associated with radial scar.

Follow-up—Of the five patients who did not undergo surgical excision (5/32 [16%]), one with a mass proven to be flat epithelial atypia at ultrasound-guided automated 14-gauge biop-

sy underwent an ultrasound-guided vacuum-assisted biopsy (10 gauge) yielding columnar cell changes with no atypia. A follow-up ul-trasound performed 1 year later did not show any residual mass. Four patients with small clusters of microcalcifications totally removed during the stereotactically guided biopsy were followed up with mammography at 12, 12, 12, and 18 months, respectively, with no significant change documented.

Imaging Characteristics of Upgraded LesionsFour carcinomas, three DCIS and one DCIS

with a focus of IDC, were discovered at surgi-cal excision. Characteristics of the upgraded lesions are summarized in Tables 3 and 4.

The DCIS with a focus of IDC presented mammographically as a mass with obscured margins (breast composition pattern 3) with-

out associated microcalcifications and was found in a patient with no personal history of breast cancer. On ultrasound, it appeared as a 1.6-cm irregular shape mass with microlobu-lated margins and complex echotexture (Fig. 4). The biopsy was performed under ultra-sound guidance.

Of the three lesions upgraded to DCIS, one presented mammographically as amorphous and another as pleomorphic microcalcifica-tions (Fig. 1). The third lesion presented as a mass with obscured margins that displayed an irregular shape and microlobulated margins at sonographic examination (7 mm).

DiscussionThe frequency of pure flat epithelial atyp-

ia arising from stereotactically and sonograph-ically guided needle biopsies in our study was

TABLE 1: Analysis of Microcalcifications Yielding Flat Epithelial Atypia on Stereotactically Vacuum-Assisted Breast Biopsy, According to BI-RADS Lexicon

CharacteristicNo. (%) of Microcalcifications

(n = 20)

Shape

Amorphous 13 (65)

Coarse heterogeneous 5 (25)

Fine pleomorphic 2 (10)

Fine linear (with or without branching) 0

Punctate 0

Distribution

Scattered 0

Regional 0

Segmental 3 (15)

Clustered 14 (70)

Linear ductal 3 (15)

Size (mm)

≤ 5 10 (50)

6–10 6 (30)

> 10 4 (20)

Degree of removal

Complete 8 (40)

Incomplete 12 (60)

TABLE 2: Sonographic Findings of Masses Yielding Flat Epithelial Atypia on Core Biopsy, According to BI-RADS Lexicon

Characteristic No. (%) of Masses (n = 9)

Shape

Irregular 6 (67)

Round 1 (11)

Oval 2 (22)

Margins

Circumscribed 2 (22)

Microlobulated 5 (56)

Indistinct 2 (22)

Angular 0

Spiculated 0

Orientation

Parallel 7 (78)

Not parallel 2 (22)

Lesion boundary

Abrupt interface 5 (56)

Echogenic halo 4 (44)

Echo pattern

Hypoechoic 4 (44)

Isoechoic 2 (22)

Complex 3 (33)

Anechoic 0

Hyperechoic 0

Posterior acoustic features

None 8 (89)

Enhancement 1 (11)

Posterior shadowing 0

Combined 0


Solorzano et al.

2.4%, in comparison with 1.5% in a recent multiinstitutional study that included both stereotactically and sonographically guided needle biopsies [9]. When considering the stereotactically guided biopsies in our sam-ple, the frequency of pure flat epithelial atypia increases to 9%, whereas pathologic and ra-diologic series have reported the frequency of pure flat epithelial atypia ranging from 3.6% to 7.6% [10–13].

Radiologic description of flat epithelial atypia is scant in the literature [14, 15]. Flat epithelial atypia most often presents at diag-nosis as microcalcifications [4, 7, 10, 14, 16–19]. Our study shows that pure flat epithe-

lial atypia presenting as microcalcifications lacks specific features. The microcalcifica-tions are most often amorphous (65%) but could be coarse heterogeneous and fine pleo-morphic. Berg et al. [20] showed that clus-tered amorphous calcifications were associ-ated with a 20% rate of malignancy and 20% rate of high-risk disease. Their series did not include flat epithelial atypia lesions, probably because of the time period during which they performed their study (1995–2000) [20]. In keeping with the recent study of Senetta et al. [16], none of the calcifications displayed a suspicious fine branching shape. Two patients showed distortions on mammography and ul-

trasound without an underlying visible mass and yielded pure flat epithelial atypia on ul-trasound-guided 14-gauge core-needle biop-sy. Both lesions were subsequently surgical-ly excised [21]. One of them yielded only flat epithelial atypia associated with fibroadeno-matous changes, whereas the other was asso-ciated with ADH and radial scar. To the best of our knowledge, sonographic descriptions of flat epithelial atypia have not been report-ed previously. In the present study, flat epi-thelial atypia presented mainly as irregular masses with microlobulated margins. Inter-estingly, this appearance is close to descrip-tions of DCIS and ADH on ultrasound [22, 23]. The ultrasound findings associated with the cases of flat epithelial atypia are not spe-cific and should not suggest that flat epitheli-al atypia is a likely diagnosis. The ultrasound features would only serve to place the lesion into BI-RADS category 4.

The surgical management of pure flat ep-ithelial atypia lesions (lacking high-risk le-sions such as ADH and lobular neoplasia) on imaging-guided needle biopsies remains controversial, with little data in the literature to support either surveillance or excision [9, 11, 24, 25]. In our study, in four of the 28 patients (14%) who underwent surgical ex-cision, the diagnosis of flat epithelial atyp-ia was an underestimation of cancer, which was close to the 13% rate reported by Lavoué et al. [9] and in keeping with other studies showing upgrade to carcinoma between 0% and 21% [4, 11, 17, 18].

The underestimation occurred regardless of the biopsy method (two under stereotac-tic guidance and two under ultrasound guid-ance). With respect to the lesions biopsied un-der ultrasound, they appeared as irregularly

TABLE 4: Characteristics of Patients With Sonographic Masses Diagnosed as Flat Epithelial Atypia at Ultrasound-Guided Biopsy and Yielding Carcinoma at Surgical Excision

Age (y) Relevant Clinical Information

Mass Size (cm)

Mass Shape Mass Margins Mass Echotexture

Mass Orientation

Posterior Acoustic Surgical Pathology

63 None 1.6 Irregular Microlobulated Complex Parallel None DCIS plus focus IDC

65 Ipsilateral breast cancer and remote breast cancer

0.7 Irregular Microlobulated Hypoechoic Parallel None DCIS

Note—DCIS = ductal carcinoma in situ, IDC = infiltrating ductal carcinoma.

A B

Fig. 4—63-year-old asymptomatic woman. A, Left craniocaudal view mammogram shows mass (arrow) with obscured margins, without associated microcalcifications. B, Sonogram shows mass (arrows) with irregular shape, microlobulated margins, complex echotexture, and parallel orientation. Sonographically guided 14-gauge core-needle biopsy yielded flat epithelial atypia. Surgical excision pathology revealed ductal carcinoma in situ with focus of invasive ductal carcinoma.

TABLE 3: Characteristics of Patients With Microcalcifications Diagnosed as Flat Epithelial Atypia at Imaging-Guided Biopsy and Yielding Carcinoma at Surgical Excision

Age (y) Relevant Clinical InformationBreast

Density TypeShape of

CalcificationsDistribution of Calcifications Size (cm) Degree of Removal (%) Surgical Pathology

49 None 2 Fine pleomorphic Segmental 4 20 DCIS

63 Contralateral breast cancer 2 Amorphous Clustered 0.4 100 DCIS

Note—DCIS = ductal carcinoma in situ.



shaped masses with microlobulated margins and complex or hypoechoic echotexture (two DCIS lesions, one with a focus of IDC). A diagnosis of flat epithelial atypia after needle biopsy of a breast mass was considered dis-cordant in our practice, and surgical excision was recommended. Only one patient under-went a subsequent 10-gauge vacuum-assist-ed biopsy under ultrasound after a 14-gauge core-needle biopsy of a small mass, allowing a complete excision of the lesion. Of inter-est is the high percentage of upgrade for flat epithelial atypia lesions appearing as mass-es at ultrasound. These results are similar to those of recent studies reporting a significant rate of underestimation when ADH is diag-nosed at ultrasound-guided 14-gauge biop-sies [23]. Underestimation of malignancy can be related to the use of 14-gauge needles instead of 11- and 10-gauge vacuum-assisted devices and to the smaller number of sam-ples retrieved, as opposed to almost com-plete removal of the lesion with vacuum-as-sisted biopsy [26]. Obtaining larger samples with larger needles might improve accuracy of the technique [27]. On the basis of our ex-perience, we recommend surgical excision of all flat epithelial atypia lesions presenting as masses at ultrasound examination.

We had two flat epithelial atypia lesions presenting as microcalcifications upgrad-ed to DCIS. One presented as a small clus-ter (0.4 cm) completely removed at biopsy in a patient with a synchronous contralater-al breast carcinoma. The other lesion was a large segmental area of calcifications (4 cm) with residual postbiopsy microcalcifications. Our finding contradicts recent studies that reported that the underestimation rate corre-lated with the percentage of removal of calci-fications and that clusters of microcalcifica-tions smaller than 1 cm completely removed by biopsy were not associated with carci-nomas [13]. The causes of underestimation in these two patients are uncertain. Intra-lesional histologic heterogeneity can lead to false-negative results at needle biopsy [28–30]. Another explanation is that malignant tumors might develop incidentally adjacent to calcifications in benign tissue and conse-quently are missed during biopsy [31]. This result emphasizes the importance of risk fac-tors such as history of breast carcinoma in the final management of biopsied lesions, even after benign results [32].

Our study has several limitations. First, our study population is small and based on a retrospective review of a single institution.

Second, our pathologic results have not been reviewed in consensus; the results shown above were based on the initial reports of our pathologist, and a review by two expert pa-thologists would have been preferable. The evaluation of flat epithelial atypia by pathol-ogists has shown moderate-to-substantial in-terobserver reproducibility [33, 34]. A third limitation of our study is that, despite the fact that most of our patients (27/32 [84%]) underwent surgical excision, not all of them had surgical correlation, which introduced a selection bias. In addition, the duration of the follow-up period in our study was 1 year. A more optimal duration of follow-up would be a 3-year minimum.

In conclusion, mammographic and sono-graphic presentations of flat epithelial atyp-ia are not specific. Mammographically, flat epithelial atypia lesions are far more like-ly to have amorphous calcifications than other shapes. Sonographically, the appear-ance shows some similarities with ADH and DCIS. Although larger studies of pure flat epithelial atypia are necessary, given the un-derestimation rate, surgical excision should be considered when imaging-guided needle biopsy yields pure flat epithelial atypia.

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Flat Epithelial Atypia of the Breast: Pathological-Radiological Correlation