Mucocele-Like Tumors of the Breast as Cystic Lesions: Sonographic-Pathologic Correlation

Women s Imaging Original Research Kim et al. Breast Tumors as Cystic Lesions Women s Imaging Original Research WOMEN S IMGING Sun Mi Kim 1,2 Hak Hee Kim 1 Doo Kyung Kang 3 Hee Jung Shin 1 Nariya Cho 4 Jeong Mi Park 5 Joo Hee Cha 1 Kim SM, Kim HH, Kang DK, et al. Keywords: breast neoplasms, mammography, ultrasound DOI:10.2214/JR.10.5028 Received May 25, 2010; accepted after revision November 1, 2010. 1 Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, san Medical Center, 388-1 Pungnap-dong, Songpa-Gu, Seoul 138-736, South Korea. ddress correspondence to H. H. Kim (hhkim@amc.seoul.kr). 2 Department of Radiology, Seoul National University Bundang Hospital, Seongnam-Si, South Korea. 3 Department of Diagnostic Radiology, jou University, College of Medicine, Suwon, South Korea. 4 Department of Diagnostic Radiology, Seoul National University, Seoul, South Korea. 5 Department of Radiology, Division of Breast Imaging and Intervention, University of Iowa Hospitals, Iowa City, I. JR 2011; 196:1424 1430 0361 803X/11/1966 1424 merican Roentgen Ray Society Tumors of the Breast as Cystic Lesions: Sonographic-Pathologic Correlation OBJECTIVE. The purpose of this study was to evaluate the differential radiologic findings of pure mucocele-like tumor and mucocele-like tumor associated with atypical ductal hyperplasia (DH) or malignancy of the breast according to BI-RDS and sonographic cystic mass classification. MTERILS ND METHODS. During a 10-year period, 72 mucocele-like tumors in 68 women were diagnosed histologically at three institutions. We retrospectively reviewed the mammographic (n = 69) and ultrasound (n = 72) findings of the 72 lesions according to the BI-RDS lexicon. The radiologic findings were correlated with the pathologic results. RESULTS. Mammography showed 53 lesions had calcifications without (n = 39) or with (n = 14) a mass. Calcifications of intermediate concern or associated with higher probability of malignancy were found more frequently in mucocele-like tumors associated with DH or malignancy than in pure mucocele-like tumors (92.3% vs 62.9%, p = 0.019). t ultrasound, 69 of the mucocele-like tumors (95.8%) were seen as a cystic mass. Cysts with thick septations, clustered cysts, and complex masses were more frequently seen in mucocele-like tumors associated with DH or malignancy (89.7% vs 32.5%, p < 0.001). The positive predictive value for BI-RDS category 4 was 13.3% (95% CI, 6.9 24.2%) and was 50% for BI-RDS category 5 (95% CI, 15 85%). CONCLUSION. Mucocele-like tumors associated with DH or malignancy were more frequently seen as clustered cysts, cysts with thick septations, and complex masses associated with calcifications of intermediate concern or higher probability of malignancy. BI-RDS can be used in the management of mucocele-like tumors. mucocele-like tumor of the breast is an unusual benign lesion. In 1986, Rosen [1] initially described mucocele-like tumor as a benign lesion. Since the early 1990s, there have been several reports on mucocele-like tumors associated with atypical ductal hyperplasia (DH) or carcinoma, or a pathologic continuum of mucinous lesions has been suggested [2 4]. Because mucocele-like tumors may be associated with these other conditions, it is difficult to differentiate a pure mucocele-like tumor from a malignant tumor with fine-needle aspiration or core needle biopsy findings, and complete excision is recommended [5 9]. Descriptions of sonographic findings of mucocele-like tumor are limited, and fewer than 20 cases have been described [7, 9]. mucocele-like tumor has been described as a cystic mass [7, 9], a finding that correlates with the pathologic finding of mucocele-like tumors as multiple cysts of mucinous material that have ruptured and discharged contents into the surrounding stroma [1]. Previous reports on the imaging findings of mucocele-like tumors described no specific findings to discriminate mucocele-like tumors associated with and those not associated with DH or malignancy [5 7, 9, 10]. It has been suggested that on mammograms, mucocele-like tumors associated with malignancy have microcalcifications more frequently and to a greater extent than do benign mucocele-like tumors [7, 11]. Two reports [12, 13] have described attempts to differentiate benign and malignant cystic lesions in various pathologic conditions. The purpose of our study was to review the mammographic and sonographic findings of mucocele-like tumors and to correlate the imaging findings with the pathologic findings. secondary purpose was to evaluate the differential radiologic findings of pure mucocelelike tumors and mucocele-like tumors associated with DH or malignancy of the breast 1424 JR:196, June 2011

Breast Tumors as Cystic Lesions according to BI-RDS [14] and the sonographic cystic mass classification described by Berg and colleagues [13]. Materials and Methods Patients and Lesions Institutional review board approval was obtained for this retrospective study, and the requirement for informed consent requirement was waived. During a 10-year period, 72 mucocele-like tumors were histologically diagnosed in 68 women (age range, 24 69 years; mean, 40 years). Fifty-four lesions were clinically occult and 18 were symptomatic: a palpable mass in 14 cases, bloody nipple discharge in three cases, and pain in one case. The initial pathologic diagnosis was made with ultrasoundguided core biopsy of 41 lesions and ultrasoundguided fine-needle aspiration biopsy of 15 lesions. The initial core biopsy results were mucocele-like tumor in 28 cases, fibrocystic change in eight cases, and DH, columnar cell hyperplasia, micropapillary hyperplasia, mucinous cancer, and papilloma in one case each. The initial fine-needle aspiration biopsy result on all 15 lesions was suggestive of mucinous neoplasm owing to the presence of abundant mucin materials. On the basis of initial biopsy results and clinical findings, all patients underwent further biopsy. The final pathologic diagnosis was established after surgical excision of 67 lesions and after ultrasound-guided vacuum-assisted biopsy (Mammotome Biopsy System, Devicor) of five lesions. fter ultrasound-guided vacuum-assisted biopsy, the lesions were no longer visualized on follow-up mammograms or ultrasound images. Of the 72 lesions, 40 were pure mucocele-like tumors, 22 were associated with DH, and 10 were associated with malignancy (eight, ductal carcinoma in situ; two, mucinous carcinoma). Imaging Techniques Sixty-five patients underwent bilateral four-view mammography (craniocaudal and mediolateral oblique views) with a dedicated unit (Senographe 600T, DMR, or 2000D, GE Healthcare). Screening mammography was performed in 48 cases and diagnostic mammography in 17 cases. Spot magnification and compression views of the lesions were obtained for evaluation of microcalcifications. ll 68 patients underwent breast ultrasound (Ultramark 9 HDI, HDI 5000, or IU22 system, dvanced Technology Laboratories) with a 10- to 12- or 14- to 16-MHz linear transducer. Eleven ultrasound examinations were performed for screening of breasts found dense at mammography, 52 for evaluation of mammographic abnormalities, four because of palpable lumps, and one because of nipple discharge. Bilateral whole-breast ultrasound was performed routinely because of the prevalence of dense parenchyma in the patient population, sometimes coupled with a personal or family history of breast cancer. With the patient supine, sonography was performed by one of five radiologists with 3 15 years of experience in breast imaging. To evaluate C for the presence of calcifications associated with sonographically detected masses, a radiopaque BB marker was placed over the skin at the site of the sonographic lesion, and additional mammography was performed (Fig. 1). Specimen radiography Fig. 1 45-year-old woman with mucocele-like tumor and atypical ductal hyperplasia., Left craniocaudal mammogram shows segmental pleomorphic microcalcifications (arrows). B, Transverse ultrasound image shows clustered microcysts (arrows). C, Left magnification compression mammogram with skin marker at mass found with ultrasound shows that calcifications (arrows) are correlated. D, Photomicrograph (H and E, 40) shows multiple dilated ducts full of mucin and focally lined by atypical ductal hyperplasia (arrows). B D JR:196, June 2011 1425

Kim et al. was performed after percutaneous needle biopsy. For the patients who underwent ultrasound-guided hookwire localization, mammography of the specimen was performed after surgical excision (Fig. 2). Imaging and Interpretation Sixty-nine lesions were examined with both mammography and sonography, and three lesions were examined with sonography only. Without knowledge of the clinical information and pathologic results, two radiologists with 17 and 8 years of experience who specialized in breast imaging retrospectively reviewed the mammographic and ultrasound images and recorded features in consensus using the BI-RDS lexicon and the ultrasound cystic mass classification described by Berg and colleagues [13, 14]. The decision about category was based on the highest level of mammographic or sonographic findings. The mammographic findings were evaluated for presence or absence of a mass, asymmetry, and microcalcifications. Masses were described by shape, margin, and density. Microcalcifications were described by type and distribution [14]. Fig. 2 34-year-old woman with bilateral mucocelelike tumors with micropapillary intraductal carcinoma., Right craniocaudal mammogram shows variably sized clustered round microcalcifications (arrows). B, Longitudinal ultrasound image shows indistinct complex mass (arrows) associated with microcalcifications in right breast 12 o clock position axis. C, Right mediolateral oblique mammogram obtained after ultrasound-guided wire localization shows sonographic mass correlated with microcalcifications (arrow). D, Specimen radiograph confirms excision microcalcifications (arrows). E, Photomicrograph (H and E, 40) shows dilated duct full of mucin and lined by malignant epithelium. B D The ultrasound features analyzed included the presence or absence of a mass and calcifications. Masses were described by shape, orientation, margin, lesion boundary, echo pattern, and posterior acoustic features. mass with a cystic appearance was classified as a simple cyst, complicated cyst, clustered microcysts, cyst with thin or thick septations, or a complex mass [13]. Simple cysts were defined as anechoic masses with an imperceptible circumscribed border and acoustic enhancement. Complicated cysts were defined as lesions with homogeneous low-level echoes that otherwise met the criteria for a simple cyst [15]. Complicated cysts could also have fluid-fluid or fluid-debris levels that might shift with changes as a result of patient position [14]. Septations within a cyst were defined as thin (< 0.5 mm, representing the combined thickness of two myoepithelial and epithelial cell layers) or thick ( 0.5 mm) [13]. cluster of tiny anechoic foci, each smaller than 2 3 mm in diameter with thin (< 0.5 mm) intervening septations and no discrete solid components was termed clustered microcysts [14]. Complex masses had both solid and cystic components [14]. Calcifications were described as macrocalcifications or microcalcifications in or out of the mass [14]. Statistical nalysis ll of the findings were analyzed with SPSS statistical software (version 15.0, SPSS). The statistical significance of differences in imaging findings between two groups pure mucocele-like tumors and mucocele-like tumors associated with DH or malignancy were calculated with the Fisher exact test. Two-tailed p 0.05 was considered statistically significant. Positive predictive value (number of cases of cancer divided by the total number of mucocele-like tumors per category 100) was calculated for every BI-RDS category to evaluate the performance of BI-RDS classification. Results Mammographic Findings Mammograms were available for 38 pure mucocele-like tumors, 21 mucocele-like tumors with DH, and 10 mucocele-like tumors C E 1426 JR:196, June 2011

Breast Tumors as Cystic Lesions with malignancy (Table 1). Thirty of 38 pure mucocele-like tumors, 17 of 21 mucocele-like tumors with DH, and nine of 10 mucocelelike tumors with malignancy had abnormal findings. The most common finding of calcifications was seen in 39 of 69 mucocele-like tumors (56.5%). Nineteen of these 39 lesions were pure mucocele-like tumors, 14 were mucocele-like tumors with DH, and six were mucocele-like tumors with malignancy. Fourteen lesions (20.3%) were masses with calcifications. Of these 14 lesions, eight lesions were pure mucocele-like tumors (Fig. 3), three were mucocele-like tumors with DH, and three were mucocele-like tumors with malignancy. Noncalcified masses were seen in only three cases of pure mucocele-like tumors. Intermediate concern or higher probability of malignant calcifications were more frequently found in mucocele-like tumors with DH or mucocele-like tumors with malignancy than in pure mucocele-like tumors (24/26 [92.3%] vs 17/27 [62.9%]; p = 0.019) (Figs. 1 and 2). Mucocelelike tumors associated with DH or mucocelelike tumors with malignancy more frequently exhibited clustered or segmental extent of microcalcifications than did benign mucocelelike tumors (24/26 [92.3%] vs 17/27 [62.9%]; p = 0.019). circumscribed oval or lobular isodense mass was most commonly seen for pure mucocele-like tumors (10/11 [90.9%] vs 2/6 [33.3%]; p = 0.027) and an indistinct irregular high-density mass for mucocele-like tumors with DH or malignancy (4/6 [66.6%] vs 1/11 [9.1%]; p = 0.027). ll 13 mammographically occult mucocele-like tumors were detected on ultrasound images as a mass and were found in patients with heterogeneously dense or extremely dense mammographic patterns. TBLE 1: Radiologic Versus Pathologic Findings Radiologic Finding Ultrasound Findings ll 72 mucocele-like tumors were seen as a mass on sonograms (Table 2). Sixty-nine mucocele-like tumors were seen as cystic masses (95.8%) and three as solid masses (4.2%). Two mucocele-like tumors with invasive mucinous carcinoma and one mucocele-like tumor with DH were visualized as solid masses. Most of the masses were circumscribed (52/72 [72.2%]), were oval (43/72 [59.7%]), were hypoechoic (38/72 [52.8%]), had parallel orientation (69/72 [95.8%]), had a thin boundary (69/72 [95.8%]), and had posterior acoustic enhancement (54/72 [75%]). n oval mass was more frequently seen for pure mucocele-like tumors than for mucocele-like tumors with DH or malignancy (31/40 [77.5%] vs 12/32 [37.5%]; p < 0.001) (Fig. 3). There were no statistically significant differences in mass orientation, margin, boundary, echogenicity, posterior acoustic features, or calcification. However, echogenic halo (n = 3) and architectural distortion (n = 2) were found only in mucocele-like tumors with DH or malignancy. Three of the 69 cystic lesions were classified as simple cysts, nine as complicated cysts, 18 as cysts with thin septations, nine as clustered microcysts, 22 as cysts with thick septations, and eight as a complex mass (Table 1). Regarding cyst patterns found in mucocele-like tumors associated with DH or malignancy, clustered cysts, cysts with thick septations, and complex masses were more frequently seen in mucocele-like tumors with DH or malignancy than in pure mucocele-like tumors (26/29 [89.7%] vs 13/40 [32.5%]; p < 0.001) (Figs. 1 and 2). Simple cysts, complicated cysts, and cysts with thin Tumor With typical Ductal Hyperplasia With Mammographic appearance (n = 69) No visible abnormality a 8 (11.6) 4 (5.8) 1 (1.4) 13 (18.8) Mass 3 (4.3) 0 0 3 (4.3) Calcifications 19 (27.5) 14 (20.3) 6 (8.7) 39 (56.5) Mass with calcifications 8 (11.6) 3 (4.3) 3 (4.3) 14 (20.3) Total 38 (55.1) 21 (30.4) 10 (14.5) 69 (100) b Sonographic appearance (n = 72) Simple cyst 2 (2.8) 1 (1.4) 0 3 (4.2) Complicated cyst 8 (11.1) 1 (1.4) 0 9 (12.5) Cyst with thin septation c 17 (23.6) 1 (1.4) 0 18 (25) Clustered microcysts 3 (4.2) 3 (4.2) 3 (4.2) 9 (12.5) Cyst with thick septation d 9 (12.5) 9 (12.5) 4 (5.6) 22 (30.6) Complex mass 1 (1.4) 6 (8.3) 1 (1.4) 8 (11.1) Solid mass 0 1 (1.4) 2 (2.8) 3 (4.2) Total 40 (55.6) 22 (30.6) 10 (13.9) 72 (100) BI-RDS final assessment category (n = 72) 2 1 (1.4) 0 0 1 (1.4) 3 6 (8.3) 1 (1.4) 0 7 (9.7) 4 33 (45.8) 19 (26.4) 8 (11.1) 60 (83.3) 5 0 2 (2.8) 2 (2.8) 4 (5.6) Total 40 (55.6) 22 (30.6) 10 (13.9) 72 (100) Note Data are number of lesions with percentage in parentheses. a Mammographically occult mucocele-like tumors were found in patients with heterogeneously or extremely dense mammographic parenchymal patterns. b Mammograms of three patients were not available for review. c Thin septations were defined as < 0.5 mm. d Thick septations are defined as 0.5 mm. Total septations were more frequently seen in pure mucocele-like tumors than in mucocele-like tumors with DH or malignancy (27/40 [67.5%] vs 3/29 [10.3%]; p < 0.001). BI-RDS Categorization For combined analysis based on mammographic and sonographic findings, one lesion was classified as category 2; seven, category 3; 60, category 4; and four, category 5 (Table 1). The positive predictive value for BI-RDS category 4 was 13.3% (CI, 6.9 24.2%) and for BI-RDS category 5 was 50% (CI, 15 85%). ll mucocele-like tumors with malignancy were classified as category 4 or 5. Because the decision about final category was based on the highest-level mammographic or sonographic finding, only one of three mucocelelike tumors visualized as simple cysts on ultrasound images was classified as category 2; JR:196, June 2011 1427

Kim et al. the other two lesions exhibited calcifications on mammograms (Table 3). ll clustered microcysts were classified as category 4 because they were associated with coarse heterogeneous or amorphous microcalcifications (Fig. 1 and Table 3). ll clustered microcysts were associated with a suspicious calcification, and there were no clustered microcysts that were not associated with a suspicious calcification. Discussion Mucocele-like tumor is a rare benign breast disease, and only limited radiologic findings have been reported [1, 5, 7, 9, 10]. In 1986, Rosen [1] first described mucocelelike tumor of the breast as a cyst of the breast containing mucinous material that had ruptured into the surrounding stroma, analogous to a mucocele of the minor salivary glands. The pathogenesis of mucocele-like tumor remains uncertain. Excess mucin secretion or ductal obstruction may contribute. Sufficiently distended cysts can be ruptured, and TBLE 2: Ultrasound Versus Pathologic Findings Ultrasound Finding extravasation of the secretions can occur by incidental trauma during daily activity. t gross inspection, mucocele-like tumors can be described as multicystic or multiloculated lesions. Microscopic inspection shows multiple aggregated cysts in fibrous stroma [1]. The cysts are lined by flat or cuboidal epithelium. The mucin pool has undergone dystrophic calcification, which causes the calcifications visualized on mammograms [5, 7, 9 11, 16, 17]. Known radiologic findings of mucocelelike tumor reflect the pathologic findings but are nonspecific, including indeterminate or suspicious microcalcifications on mammograms and the presence of cysts with calcified or noncalcified mural nodules [5, 7, 9, 10]. The most common radiologic feature of a mucocele-like tumor was the presence of a cystic mass on ultrasound images with or without microcalcifications depicted on mammograms, which is similar to findings described in previous reports [7, 9]. Sixty- Tumor (n = 72) With typical Ductal Hyperplasia With Shape Oval 31 (43.1) 10 (13.9) 2 (2.8) 43 (59.7) Irregular 9 (12.5) 12 (16.7) 8 (11.1) 29 (40.3) Orientation Parallel 39 (54.2) 20 (27.8) 10 (13.9) 69 (95.8) Not parallel 1 (1.4) 2 (2.8) 0 3 (4.2) Margin Circumscribed 32 (44.4) 13 (18.1) 7 (9.7) 52 (72.2) Indistinct 8 (11.1) 9 (12.5) 3 (4.2) 20 (27.8) Boundary Thin 40 (55.6) 21 (29.2) 8 (11.1) 69 (95.8) Echogenic halo 0 1 (1.4) 2 (2.8) 3 (4.2) Echogenicity nechoic 22 (30.6) 10 (13.9) 2 (2.8) 34 (47.2) Hypoechoic 18 (25) 12 (16.7) 8 (11.1) 38 (52.8) Posterior acoustic feature Enhancement 32 (44.4) 13 (18.1) 9 (12.5) 54 (75) No enhancement 8 (11.1) 9 (12.5) 1 (1.4) 18 (25) rchitectural distortion 0 1 (1.4) 1 (1.4) 2 (2.8) Calcification Macrocalcification 21 (29.2) 12 (16.7) 3 (4.2) 36 (50) Microcalcification 2 (2.8) 3 (4.2) 3 (4.2) 8 (11.1) Note Data are number of lesions with percentage in parentheses. Total nine of the mucocele-like tumors (95.8%) were seen as a cystic mass on ultrasound images. Most of the masses had benign features, including a circumscribed border, oval shape, anechoic nature with parallel orientation, thin boundary, and posterior acoustic enhancement. These findings are nonspecific, but when microcalcifications are detected on mammograms and cystic lesions are detected on ultrasound images, the differential diagnosis of mucocele-like tumor can be considered. The presence of a mucocele-like tumor has been emphasized by known association with DH and mucinous carcinoma [4, 11]. spectrum of change that represents a pathway of progression from mucin-filled ducts through DH and ductal carcinoma in situ to invasive mucinous carcinoma has been suggested [2 4]. Because it is difficult to differentiate a pure mucocele-like tumor from a mucinous tumor at cytologic examination and because of underestimation at core biopsy, excision is recommended when mucocele-like tumor is diagnosed [2, 4, 8]. The reported radiologic findings provide no specific suggestions for differentiating pure from malignancy-associated mucocele-like tumors, except that on mammograms malignancy-associated mucocele-like tumors more frequently contain microcalcifications of wider extent than those in benign mucocele-like tumors [7, 11]. To the best of our knowledge, there has been no report on the use of sonographic findings to differentiate pure from malignancy-associated mucocele-like tumors. Two studies [12, 13] have been conducted to differentiate benign and malignant cystic lesions from various pathologic conditions. The presence of malignancy was not proved for simple cysts, complicated cysts, cysts with thin septations, or clustered microcysts. Complex masses were found to have 23 44% malignant potential. In our study, mucocele-like tumors seen as simple cysts, complicated cysts, or cysts with thin septations were not associated with malignancy. Mucocele-like tumors associated with malignancy were seen as clustered cysts, cysts with thick septations, or complex masses. The prevalence of malignancy was 33.3% for clustered cysts, 18.2% for cysts with thick septations, and 12.5% for complex masses. However, the results are conditional because of the small number of lesions. It is noteworthy that 54.5% of cysts with thick septations and 62.5% of complex masses were associated with suspicious calcifications. In a comparison with stud- 1428 JR:196, June 2011

Breast Tumors as Cystic Lesions TBLE 3: Ultrasound Findings Versus ppearance of Calcifications Mammographic ppearance of Calcifications (n = 53) Typical Benign Intermediate Concern Higher Probability of Total typical Ductal Hyperplasia Tumor typical Ductal Hyperplasia Tumor Tumor With typical Ductal Hyperplasia Tumor Ultrasound ppearance Simple cyst 1 (1.9) 0 0 0 1 (1.9) 0 0 0 0 2 (3.8) Complicated cyst 1 (1.9) 0 0 3 (5.7) 1 (1.9) 0 0 0 0 5 (9.4) Cyst with thin septation 6 (11.3) 0 0 7 (13.2) 0 0 0 0 0 13 (24.5) Clustered microcysts 0 0 0 3 (5.7) 3 (5.7) 3 (5.7) 0 0 0 9 (17) Cyst with thick septation 2 (3.8) 2 (3.8) 0 4 (7.5) 2 (3.8) 2 (3.8) 0 3 (5.7) 1 (1.9) 16 (30.2) Complex mass 0 0 0 0 4 (7.5) 1 (1.9) 0 0 0 5 (9.4) Solid mass 0 0 0 0 1 (1.9) 1 (1.9) 0 0 1 (1.9) 3 (5.7) Total 10 (18.9) 2 (3.8) 0 17 (32.1) 12 (22.6) 7 (13.2) 0 3 (5.7) 2 (3.8) 53 (100) Note Data are number of lesions with percentage in parentheses. ies by Berg et al. [13] and Chang et al. [12], the only difference in our study is in regard to clustered cysts associated with malignancy. Clustered cysts usually can be considered probably benign, having less than 2% malignant potential, and can be followed up when the patient has no symptoms [12, 13]. However, in our study, three mucocele-like tumors associated with malignancy seen as clustered cysts at sonography were seen as suspicious microcalcifications at mammography. Therefore, clustered cysts with microcalcifications that suggest mucocele-like tumor should be subjected to core biopsy; noncalcified clustered cysts, however, should be regarded as category 3. In our study, the presence of microcalcifications without a mass was the most common mammographic finding of mucocele-like tumors. Including microcalcifications associated with a mass, 76.8% of mucocele-like tumors were seen as microcalcifications. Of these microcalcifications, 77.4% of the mucocele-like tumors were seen as intermediate concern or higher possibility of malignant microcalcification. Intermediate concern and higher probability of malignant calcifications are more frequently found in mucocele-like tumors with DH or malignancy than in pure mucocele-like tumors. Mammographically occult mucocele-like tumors were found in patients with heterogeneous or extremely dense parenchymal patterns at mammography. For the treatment of mucocele-like tumors, Hamele-Bena et al. [11] suggested that excisional biopsy is sufficient for benign mucocele-like tumors and that breast-conserving surgery is appropriate for mucocele-like tumors combined with carcinoma. The current pathologic recommendation is that surgical excision is warranted after core biopsy of a lesion that is suggestive of a possible mucocele-like tumor [8]. Our series also had a high rate (44.4%) of mucocele-like tumors combined with DH or a malignant tumor. This high rate of mucocelelike tumors associated with these other lesions supports the current pathologic recommendation for complete excision. However, BI-RDS is useful for managing mammographic and sonographic lesions [14]. For combined analysis based on mammographic and sonographic findings, all mucocele-like tumors with malignancy were classified as BI-RDS category 4 or 5. ll pure mucocele-like tumors were classified as category 2, 3, or 4. BI-RDS also may be useful for mucocele-like tumors, and it may be possible to manage category 2 and 3 lesions with follow-up. This study had several limitations. The cases were selected as retrospectively proved mucocele-like tumors at three institutions. Because the study was retrospective, real-time sonographic images were not available at the time of review, and sonographic findings were interpreted with static images. lthough an expert in breast ultrasound performed all of the breast ultrasound examinations, there might have been interobserver variability. To overcome interobserver variability, two investigators reviewed all of the static images retrospectively; however, some effect of operator dependency of breast ultrasound remained. prospective study is needed to overcome this limitation. Conclusion The sonographic appearances of most mucocele-like tumors of the breast are those of various cystic lesions, including simple cysts, complicated cysts, cysts with thin or thick septations, and clustered cysts and of complex masses. Most of the lesions were associated with microcalcifications as depicted at mammography. These findings are nonspecific, but when microcalcifications are detected on mammograms and a cystic lesion is visualized on ultrasound images, the differential diagnosis of mucocele-like tumor can be considered. Mucocele-like tumors associated with DH or malignancy were more frequently seen as clustered cysts, cysts with thick septations, or complex masses associated with intermediate concern or higher probability of malignant calcifications. Use of BI-RDS can facilitate the management of mucocele-like tumors. References 1. Rosen PP. Mucocele-like tumors of the breast. m J Surg Pathol 1986; 10:464 469 2. Weaver MG, bdul-karim FW, al-kaisi N. Mucinous lesions of the breast: a pathological continuum. Pathol Res Pract JR:196, June 2011 1429

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