Ultrasonographic detection and characterization of asymptomatic ductal carcinoma in situ with histopathologic correlation

Could breast multiparametric MRI discriminate between pure ductal carcinoma in situ and microinvasive carcinoma?

BACKGROUND

Ductal carcinoma in situ (DCIS) is often reclassified as invasive cancer in the final pathology report of the surgical specimen. It is of significant clinical relevance to acknowledge the possibility of underestimating invasive disease when utilizing preoperative biopsies for a DCIS diagnosis. In cases where such histologic upgrades occur, it is imperative to consider them in the preoperative planning process, including the potential inclusion of sentinel lymph node biopsy due to the risk of axillary lymph node metastasis.

PURPOSE

To assess the capability of breast multiparametric magnetic resonance imaging (MP-MRI) in differentiating between pure DCIS and microinvasive carcinoma (MIC).

MATERIAL AND METHODS

Between January 2018 and November 2022, this retrospective study enrolled patients with biopsy-proven DCIS who had undergone preoperative breast MP-MRI. We assessed various MP-MRI features, including size, morphology, margins, internal enhancement pattern, extent of disease, presence of peritumoral edema, time-intensity curve value, diffusion restriction, and ADC value. Subsequently, a logistic regression analysis was conducted to explore the association of these features with the pathological outcome.

RESULTS

Of 129 patients with biopsy-proven DCIS, 36 had foci of micro-infiltration on surgical specimens and eight were diagnosed with invasive ductal carcinoma (IDC). The presence of micro-infiltration foci was significantly associated with several MP-MRI features, including tumor size (P <0.001), clustered ring enhancement (P <0.001), segmental distribution (P <0.001), diffusion restriction (P = 0.005), and ADC values <1.3 × 10-3 mm2/s (P = 0.004).

CONCLUSION

Breast MP-MRI has the potential to predict the presence of micro-infiltration foci in biopsy-proven DCIS and may serve as a valuable tool for guiding therapeutic planning.

Surgical Outcomes for Ductal Carcinoma in Situ: Impact of Preoperative MRI

Background The role of preoperative MRI for predicting surgical outcomes in patients diagnosed with ductal carcinoma in situ (DCIS) remains uncertain. Purpose To investigate the associations between preoperative MRI and surgical outcomes in DCIS confirmed by using US-guided core-needle biopsy (CNB) and to evaluate clinical-pathologic variables associated with a benefit from MRI. Materials and Methods Women with DCIS confirmed by using US-guided CNB between January 2012 and December 2016 were included in this retrospective study. Propensity score matching using 18 confounding covariates was used to create matched groups with MRI and without MRI, and surgical outcomes were compared. Clinical-pathologic variables were evaluated to determine women who benefited from MRI. Results A total of 541 women (mean age ± standard deviation, 50 years ± 10) were evaluated. Among 430 women who underwent MRI, 67 additional lesions (16%) were depicted, with 25 (37%) of the 67 additional lesions being malignant. Fifty-seven (13%) of the 430 women had a change in surgical plan because of their MRI findings; the change was appropriate for 31 (54%) women. In matched groups, the MRI group was associated with lower odds of positive resection margin (odds ratio [OR], 0.39; 95% confidence interval [CI]: 0.16, 0.93; P = .03) and repeat surgery (OR, 0.33; 95% CI: 0.12, 0.92; P = .03) compared with the non-MRI group. There was no difference in likelihood of initial mastectomy (OR, 1.2; 95% CI: 0.7, 2.0; P = .59) and overall mastectomy (OR, 0.93; 95% CI: 0.5, 1.6; P = .79). In the MRI group, low nuclear grade (90% [28 of 31] vs 69% [275 of 399]; P = .01), progesterone receptor positivity (81% [25 of 31] vs 61% [244 of 399]; P = .03), and human epidermal growth factor receptor 2 negativity (90% [28 of 31] vs 68% [270 of 399]; P = .01) were associated with a benefit from MRI versus no MRI. Conclusion Preoperative MRI depicted additional malignancy and reduced positive surgical margins and repeat surgery for ductal carcinoma in situ confirmed at US-guided biopsy without a higher mastectomy rate. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Pinker in this issue.

Imaging features that distinguish pure ductal carcinoma in situ (DCIS) from DCIS with microinvasion

Patients with ductal carcinoma in situ with microinvasion (DCISM) have worse cancer-specific survival, disease-free survival and overall survival, and a higher mortality rate compared with patients with ductal carcinoma in situ (DCIS). Distinguishing DCISM from DCIS via preoperative imaging could help to predict the prognosis of patients. The present study compared the sonographic and mammographic features of patients with DCIS and DCISM. A total of 147 women (94 patients with DCIS and 53 patients with DCISM) were retrospectively included. The sonographic lesions were classified as either masses or non-mass abnormalities. The lesions observed on mammography were classified as calcifications only, mass, asymmetry or architectural distortion. Statistical comparisons were performed using the Mann-Whitney U test, χ² test, Fisher's exact test and multiple logistic regression analysis. Univariate and multivariate analyses showed that the presence of calcifications (P=0.038) and vascularity (P=0.025) on sonography were associated with DCISM. Furthermore, a lager distribution of calcifications was associated with a higher likelihood of DCISM (P=0.002). In conclusion, the presence of calcifications and vascularity on sonography or a lager distribution of calcifications on mammography may suggest DCISM.

Non-Mass Breast Lesions on Ultrasound: Feature Exploration and Multimode Ultrasonic Diagnosis

The aim of this study was to analyze the features of non-mass breast lesions (NMLs) on B-mode ultrasound (US), color Doppler US, strain elastography (SE) and contrast-enhanced ultrasound (CEUS) and to develop a multimode ultrasonic method for NML differentiation. Seventy-one NMLs were included in this retrospective study. Binary logistic regression was used to identify the independent risk factors. Pathology results were used as the standard criterion. Microcalcification on US, high stiffness on SE and hyper-enhanced intensity on CEUS were identified as features correlated with malignancy. A multimode method to evaluate NMLs based on the logistic regression was developed. The sensitivity and specificity for US, US + Doppler, US + SE, US + CEUS and the multimode method were 100% and 29%, 92.5% and 41.9%, 97.5% and 58.1%, 90.0% and 58.1% and 95.0% and 77.4%, respectively. The accuracy of these methods was 69.0%, 70.4%, 80.2%, 76.1% and 87.3%, respectively. The multimode ultrasonic method is simple and exhibited high diagnostic performance, which might be helpful for predicting the potential malignancy of NMLs.

Comparison of mammography, ultrasound, and MRI in size assessment of ductal carcinoma in situ with histopathologic correlation

Background The ability to accurately assess tumor size in ductal carcinoma in situ (DCIS) is an important clinical issue when selecting the appropriate treatment plan. Purpose To compare the accuracy of using mammography, ultrasound (US), and magnetic resonance imaging (MRI) to assess DCIS tumor size based on imaging and histopathological findings. Material and Methods Fifty-six patients with DCIS were included. Mammography, US, and MRI were reviewed, and the accuracy of the measured tumor sizes were compared with the imaging and histopathological parameters. Results If visible, tumor measurements demonstrated high reliability with the pathologically determined size, with the best results obtained using US ( k = 0.851) followed by mammography ( k = 0.815) and MRI ( k = 0.738). Tumor size assessment was significantly more accurate when the lesion was shown as a mass on US ( P = 0.003) or MRI ( P < 0.001) with minimal and mild background parenchymal enhancement ( P = 0.016) on MRI. When mammography was used to assess tumor size, the tumors with positive estrogen receptor status and luminal A subtype demonstrated a significantly more accurate tumor size. Conclusion The combination of US and MRI, in addition to mammography, has an important role in assessing the exact tumor extent of DCIS.

Ultrasonographic features of pure ductal carcinoma in situ of the breast: correlations with pathologic features and biological markers

Purpose

The purpose of this study was to evaluate the ultrasonographic features of pure ductal carcinoma in situ (DCIS) of the breast and to evaluate the correlations of ultrasonographic features with pathologic and biological features.

Methods

A total of 141 lesions in 138 women with pure DCIS who underwent preoperative breast ultrasonography were retrospectively reviewed. Ultrasonographic features were analyzed using the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) ultrasonography lexicon and the diagnostic criteria of the Japan Society of Ultrasonics in Medicine. Pathologic features including the nuclear grade and presence of comedonecrosis were evaluated. Biological markers including estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) status, as well as the Ki-67 index, were recorded. Ultrasonographic features were compared with pathologic findings and biological markers using the chi-square test. P-values of <0.05 were considered to indicate statistical significance.

Results

Of the 141 lesions, 75 (53.2%) were mass lesions, 56 (39.7%) were non-mass lesions, and 10 (7.1%) were not visible. The most common feature of the mass pattern was a mass with irregular shape (32.6%), an indistinct margin (27.7%), and hypoechogenicity (37.6%). Microcalcifications were observed in 48 cases (36.6%) as an associated feature. Calcifications outside of a mass were more common than calcifications within a mass. Ultrasonographic microcalcifications and ductal changes were frequently observed in non-mass lesions. Ultrasonographic non-mass lesions were associated with high-grade DCIS (P=0.004) and the presence of comedonecrosis (P=0.006). Microcalcifications were significantly associated with high-grade DCIS (P<0.001), the presence of comedonecrosis (P<0.001), an elevated Ki-67 (P<0.001), and HER2 positivity (P=0.003).

Conclusion

The most common ultrasonographic feature of pure DCIS was an irregular, hypoechoic mass with an indistinct margin. Ultrasonographic microcalcifications and ductal changes were more frequent in non-mass lesions, which were correlated with poor prognostic factors, such as a high nuclear grade, comedonecrosis, HER2 positivity, and an elevated Ki-67 index.

Association between underestimation of tumour size by imaging and incomplete excision in breast-conserving surgery for breast cancer

Background

Completeness of excision is the most important factor influencing local recurrence after breast-conserving surgery (BCS). The aim of this case–control study was to determine factors influencing incomplete excision in patients undergoing BCS.

Methods

Women with invasive breast cancer treated by BCS between 1 June 2008 and 31 December 2009 were identified from a prospectively collected database in the Edinburgh Breast Unit. The maximum size of the tumour, measured microscopically, was compared with the size estimated before operation by mammography and ultrasound imaging. A multivariable analysis was performed to investigate factors associated with incomplete excision.

Results

The cohort comprised 311 women, of whom 193 (62·1 per cent) had a complete (CE group) and 118 (40·7 per cent) an incomplete (IE group) excision. Mammography underestimated tumour size in 75·0 per cent of the IE group compared with 40·7 per cent of the CE group (P &lt; 0·001). Ultrasound imaging underestimated tumour size in 82·5 per cent of the IE group compared with 56·5 per cent of the CE group (P &lt; 0·001). The risk of an incomplete excision was greater when mammography or ultrasonography underestimated pathological size: odds ratio (OR) 4·38 (95 per cent c.i. 2·59 to 7·41; P &lt; 0·001) for mammography, and OR 3·64 (2·03 to 6·54; P &lt; 0·001) for ultrasound imaging. For every 1-mm underestimation of size by mammography and ultrasonography, the relative odds of incomplete excision rose by 10 and 14 per cent respectively.

Conclusion

Underestimation of tumour size by current imaging techniques is a major factor associated with incomplete excision in women undergoing BCS.

Sonographic Features of Ductal Carcinoma In Situ of the Breast With Microinvasion: Correlation With Clinicopathologic Findings and Biomarkers

OBJECTIVES

To compare the sonographic results, clinicopathologic characteristics, and biomarkers in pure ductal carcinoma in situ (DCIS) of the breast and DCIS with microinvasion.

METHODS

A total of 218 patients with pathologically proven DCIS based on sonography in our hospital (2009-2013) were retrospectively enrolled. Clinicopathologic characteristics and biomarkers were examined. Grayscale sonographic results were investigated according to the American College of Radiology Breast Imaging Reporting and Data System lexicon, and color Doppler sonography was used to assess the vascularization distribution and degree. All variables were compared by univariate and multivariate logistic regression analyses.

RESULTS

All patients were female, with a mean age of 55.3 years (range, 32-78 years). One hundred sixty patients with 160 lesions had pure DCIS, and 58 patients with 58 lesions had DCIS with microinvasion. Ductal carcinoma in situ with microinvasion was more likely to have sentinel lymph node metastases, larger tumors, a higher tumor grade, human epidermal growth factor receptor 2 positivity, and a high Ki-67 index (all P < .05). Univariate analysis showed that DCIS with microinvasion was more likely to be hypoechoic with microcalcifications, have a mixed vascularization distribution (equal peripheral and internal blood flow signals), and have a high degree of vascularization (at least 2 penetrating vessels; all P < .05). Multivariate analysis indicated that the presence of microcalcifications and a high degree of vascularization were significantly and independently associated with microinvasion (both P < .001).

CONCLUSIONS

Our findings suggest that DCIS with microinvasion is more likely to have microcalcifications and a high degree of vascularization than pure DCIS. Patients with these sonographic features are more likely to have a high tumor grade, sentinel lymph node metastases, larger tumors, a high Ki-67 index, and human epidermal growth factor receptor 2 positivity.

Correlation between sonographic findings and clinicopathologic and biologic features of pure ductal carcinoma in situ in 691 patients

OBJECTIVE

The objective of our study was to compare the sonographic features of pure ductal carcinoma in situ (DCIS) lesions with the initial clinical presentation and histopathologic findings.

MATERIALS AND METHODS

The images and records of 691 patients with pure DCIS who underwent preoperative mammography and whole-breast sonography as part of staging workup in a single institution from January 1, 1996, through July 31, 2009, were reviewed. The BI-RADS sonography lexicon was used when reviewing the sonographic studies. Histopathologic features recorded included estrogen receptor (ER) status, nuclear grade, and presence or absence of comedonecrosis. Statistical comparisons were made using the Student t test, chi-square test, Fisher exact test, Kruskal-Wallis or Wilcoxon rank sum test, multiple logistic regression analysis, and Pearson correlation coefficient.

RESULTS

A total of 304 (44%) tumors were visible on mammography and sonography; 315 (46%), on mammography only; 58 (8%), on sonography only; and 14 (2%), on neither mammography nor sonography. The most common sonographic appearance of DCIS was an irregular hypoechoic mass with indistinct margins and normal posterior features that was indistinguishable from invasive carcinoma. Patients with symptomatic high-nuclear-grade DCIS, dense breasts, and comedonecrosis were younger and had larger tumors on sonography than asymptomatic women with nondense breasts and low-nuclear-grade and noncomedo DCIS. Women with ER-negative DCIS were older and had larger tumors on sonography than women with ER-positive DCIS. ER-negative tumors were more frequently visible on sonography than ER-positive tumors (p=0.007). High-grade DCIS (p<0.0001) and comedo DCIS (p<0.0001) presented more frequently as microcalcifications, architectural distortion, and ductal changes on sonography than low-grade DCIS or noncomedo DCIS.

CONCLUSION

Of the 691 pure DCIS lesions, 362 (52%) were visible on sonography and presented most commonly as a mass. Lesion visibility of DCIS on sonography was not related to nuclear grade or the presence of comedonecrosis.

Non-mass-like lesions on breast ultrasound: classification and correlation with histology

PURPOSE

Owing to advances in ultrasound (US) technology, optimal US techniques with a high-frequency transducer can identify more and more breast lesions. However, some lesions show up as non-mass-like lesions, which are difficult to be correctly identified and often result in missed diagnosis and misdiagnosis. The purpose of the present study was to develop a classification of the US features of non-mass-like breast lesions correlated with pathology, so as to improve the diagnostic accuracy of US in non-mass-like breast lesions.

MATERIALS AND METHODS

A total of 854 breast lesions in 836 consecutive women scheduled for US-guided core-needle biopsy or US-guided vacuum-assisted biopsy between May 2008 and October 2011 were initially included in this study. Finally, 80 breast lesions in 78 women were classified as non-mass-like lesion and included in this study. The US features of the 80 non-mass-like breast lesions were classified and their correlation with pathology was analysed.

RESULTS

Of the 80 non-mass-like breast lesions, 43 cases (53.8 %) were malignant and 37 cases (46.2 %) were benign. Fifty-two cases (73.7 %) appeared as a hypoechoic area, 22 cases (21.1 %) appeared as a hypoechoic area with sporadic or clustered microcalcification, four cases appeared as architectural distortion, and two cases appeared as solid echogenicity within a duct. The diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive value of US for non-mass-like breast lesions were 71.25, 95.35, 43.24, 66.13 and 88.89 %, respectively. The finding of a hypoechoic area with microcalcification showed a statistically significant association with malignant lesions and its positive predictive value for carcinoma was 78.26 %.

CONCLUSION

Non-mass-like breast lesions usually appeared as a hypoechoic area or a hypoechoic area with microcalcification. The finding of a hypoechoic area with microcalcification had a close correlation with malignant lesions. US had a high sensitivity but a low specificity in the diagnosis of non-mass-like breast lesions and a definitive diagnosis requires a US-guided biopsy.

Diagnostic evaluation of ductal carcinoma in situ of the breast: ultrasonographic, mammographic and histopathologic correlations

The aims of the study described here were to illustrate the spectrum of ultrasonographic features of ductal carcinoma in situ (DCIS) and to evaluate the ability of ultrasonography (US) to predict the grade and recurrence of DCIS on the basis of mammographic and histopathologic findings. We retrospectively evaluated the ultrasonographic features of 129 DCIS lesions from 127 consecutive women and compared these with their mammographic and histopathologic features. The mean size of DCISs on ultrasonography and mammography (MMG) was 3.67 ± 1.40 and 4.00 ± 1.74 cm, respectively, which do not differ statistically (p = 0.09). Despite the statistical difference in Breast Imaging Reporting and Data System (BI-RADS) classification on US and MMG (p = 0.000), the median BI-RADS classification is category 4c on both US and MMG (p = 0.01). There was no statistically significant difference in the distribution of microcalcification on MMG and US. Clusters <5 mm in greatest diameter are easily seen on MMG. At US, a scattered/linear distribution on MMG had a higher level of visibility than clustered distribution on MMG. The correlation between tumor size and DCIS with micro-invasion evaluated using US is higher than that obtained using MMG (p = 0.001 and 0.024, respectively). When US was used for the detection of DCIS, diagnostic accuracy was significantly associated with higher Van Nuys groups, the presence of micro-invasion and comedo carcinoma (p = 0.000, 0.022 and 0.011, respectively). However, mammographic diagnostic accuracy was found not to associate with higher Van Nuys groups, the presence of micro-invasion and comedo carcinoma (p = 0.054, 0.093 and 0.256, respectively). Ultrasonography may play an important role both in detecting DCIS and in evaluating its histopathologic features. Detection of DCIS using MMG alone may be suboptimal for patients with dense breasts, especially among Chinese women.

Non-mass-like breast lesions at ultrasonography: feature analysis and BI-RADS assessment

OBJECTIVE

To analyze the features of non-mass-like (NML) breast lesions on ultrasound (US) and determine their corresponding malignancy rate and to stratify these lesion patterns according to US BI-RADS categories.

MATERIALS AND METHODS

One hundred sixty-four consecutive lesions were retrospectively classified into four types according to the US features, the corresponding positive predictive values (PPVs) were obtained. Clinical, imaging, and histopathological findings were reviewed.

RESULTS

Among the 164 lesions, 39 (24%) were classified as type Ia, 14 (8%) as type Ib, 39 (24%) as type IIa, 19 (12%) as type IIb, 19 (12%) as type III, and 34 (21%) as type IV. The PPVs for malignancy were 21% for type Ia, 79% for type Ib, 10% for type IIa, 58% for type IIb, 16% for type III, and 21% for type IV. All NML lesions were classified as BI-RADS category 4a (type IIa), 4b (type Ia, III and IV) and 4c (type Ib and IIb) according to their PPVs. There was a significantly higher frequency of malignancy among lesions of type Ib and type IIb compared with the other types (P<0.01 for each). Lesions with associated calcifications, presence of abnormal axillary nodes, or a mammographic finding of suspected malignancy had a higher probability of malignancy (P<0.05 for each).

CONCLUSION

US is useful in clarifying the indication for biopsy of NML lesions. The types of US classifications used in our study establish reliable references for the NML patterns when stratified according to the BI-RADS categories.

Nonmasslike lesions on breast sonography: comparison between benign and malignant lesions

OBJECTIVES

To compare the imaging and clinical features of benign and malignant nonmasslike lesions in the breast.

METHODS

During a 2-year period at a single institution, 186 nonmasslike lesions in 158 women were pathologically confirmed through surgery or sonographically guided biopsy. The sonographic patterns (mottled, geographic, and indistinct) and distributions (focal and regional) were compared between benign and malignant lesions. The presence of sonographically visible calcifications, amount of color Doppler signals, presence of positive findings on mammography, and presence of symptoms were also compared between the two groups.

RESULTS

A total of 156 lesions (84%) were confirmed as benign and 30 (16%) as malignant. On sonography, malignant nonmasslike lesions more frequently had mottled and geographic patterns and regional distribution than benign lesions (P < .0001). Malignant lesions also more frequently had sonographically visible calcifications (40% versus 0%; P < 0.0001) and a greater amount of color Doppler signals than benign lesions (P < .0001). On mammography, malignant lesions more frequently had densities and calcifications than benign lesions (30.4% versus 7.1%; P = 0.0052; 73.9% versus 6.1%; P < .0001, respectively). Clinically, malignant lesions were more frequently palpable and accompanied by localized pain than benign lesions (50% versus 2.6%; P< .0001; 13.3% versus 0.6%; P = .0025).

CONCLUSIONS

The imaging and clinical features of malignant nonmasslike lesions differed significantly from those of benign nonmasslike lesions.

Potential role of shear-wave ultrasound elastography for the differential diagnosis of breast non-mass lesions: preliminary report

OBJECTIVES

To report our preliminary experience with shear-wave elastography (SWE) for non-mass lesions (NMLs) in the breast and suggest a potential ancillary role of SWE for BI-RADS Category 4a NMLs in reducing the number of unnecessary benign biopsies.

METHODS

A total of 310 breast lesions in 286 consecutive women who had been scheduled for US-guided automated gun biopsy or vacuum-assisted biopsy between June and December 2012 were initially included in this study. Finally, 33 women with 34 breast lesions classified as NMLs constituted our study population. Diagnostic performances of each quantitative SWE parameter were calculated. Histological diagnosis was used as a reference standard.

RESULTS

Among the 34 breast NMLs, 22 (65%) were benign and 12 (35%) were malignant. Emean value with cut-off set at 41.6 kPa had the highest Az value 0.788 (95% CI, 0.625-0.951), showing sensitivity of 83.3% and specificity of 68.2%. By applying an Emean value of 41.6 kPa or less as a criterion for downgrading soft BI-RADS category 4a NMLs to category 3 NMLs, 15 unnecessary biopsies could have been eliminated from the 19 BI-RADS category 4a lesions (79%).

CONCLUSIONS

SWE features could increase positive predictive values and reduce unnecessary benign biopsies of category 4a NMLs.

KEY POINTS

• Ultrasound elastography is increasingly used to assess the stiffness of breast lesions • Shear-wave elastography provides useful information about non-mass breast lesions • Shear-wave elastography may render some biopsies of non-mass breast lesions unnecessary.

Ductal carcinoma in situ of the breast: a surgical perspective

Ductal carcinoma in situ (DCIS) of the breast is a heterogeneous neoplasm with invasive potential. Risk factors include age, family history, hormone replacement therapy, genetic mutation, and patient lifestyle. The incidence of DCIS has increased due to more widespread use of screening and diagnostic mammography; almost 80% of cases are diagnosed with imaging with final diagnosis established by biopsy and histological examination. There are various classification systems used for DCIS, the most recent of which is based on the presence of intraepithelial neoplasia of the ductal epithelium (DIN). A number of molecular assays are now available that can identify high-risk patients as well as help establish the prognosis of patients with diagnosed DCIS. Current surgical treatment options include total mastectomy, simple lumpectomy in very low-risk patients, and lumpectomy with radiation. Adjuvant therapy is tailored based on the molecular profile of the neoplasm and can include aromatase inhibitors, anti-estrogen, anti-progesterone (or a combination of antiestrogen and antiprogesterone), and HER2 neu suppression therapy. Chemopreventive therapies are under investigation for DCIS, as are various molecular-targeted drugs. It is anticipated that new biologic agents, when combined with hormonal agents such as SERMs and aromatase inhibitors, may one day prevent all forms of breast cancer.

Non-mass-like lesions on breast ultrasonography: a systematic review

This article reviews various non-mass-like ultrasonography (US) findings of the breast and the sonographic-pathologic correlation with Doppler techniques, elastography, and MRI. High-resolution US allows for identification of small, clinically occult non-mass-like US findings. Ductal carcinoma in situ and invasive lobular carcinoma usually manifest as a non-mass-like lesion on US. It is useful to classify non-mass-like lesions on US in a similar manner to the classification of non-mass-like enhancement on MRI.