MR features to suggest microinvasive ductal carcinoma of the breast: can it be differentiated from pure DCIS?

Abstract

Background

Morphologic and kinetic characteristics of breast lesions are regarded as a major criterion for their differential diagnosis in dynamic magnetic resonance imaging (MRI). However, there have not been well-reported MRI findings of microinvasive ductal carcinoma.

Purpose

To evaluate MRI characteristics of microinvasive ductal carcinoma of the breast and to compare MRI findings in patients with microinvasive ductal carcinoma and pure ductal carcinoma in situ (DCIS).

Material and Methods

Eighty-one patients with pathologically confirmed microinvasive ductal carcinomas (n = 37) or pure DCIS (n = 44) were included in this study. The MRI findings were analyzed without knowledge of the pathologic and conventional imaging findings. For all the lesions detected on MRI, morphologic and kinetic analyses were performed according to the Breast Imaging Reporting and Data System. For the non-mass lesions, the presence of clustered ring enhancement was also analyzed. Statistical analyses were performed using Student's t test, χ² test, and Fisher's exact test.

Results

In total 35 cases of microinvasive ductal carcinoma and 39 cases of DCIS were detected on MRI. The most common and dominant MRI findings of microinvasive ductal carcinoma and DCIS were non-mass lesions with heterogeneous enhancement. However, the spiculated margin of the mass-type lesion (P = 0.022), the segmental distribution (P = 0.023), and clustered ring enhancement (P = 0.006) of the non-mass-type lesion, and the enhancement kinetics showing strong initial enhancement (P = 0.004) with subsequent wash-out (P = 0.001) were significantly more frequent in microinvasive ductal carcinoma than in DCIS.

Conclusion

Non-mass lesions with segmental distribution, heterogeneous enhancement, and strong initial enhancement with a wash-out curve were the dominant MRI findings of microinvasive ductal carcinoma. Compared with DCIS, microinvasive ductal carcinoma showed more suspicious imaging characteristics. For the non-mass lesions, clustered ring enhancement was also a characteristic finding of microinvasion on MRI.

Keywords

Breast MR imaging neoplasms – primary microinvasion

Microinvasive ductal carcinoma is an uncommon entity accounting for <1% of all breast cancers (1, 2). According to the American Joint Committee on Cancer 7th edition of cancer staging, microinvasive ductal carcinoma of the breast was defined as ductal carcinoma in situ (DCIS) with an extension of cancer cells beyond the basement membrane and no invasive focus measuring >1 mm in the greatest dimension (3).

The widespread implementation of screening mammography has increased the incidence of early breast cancer, including DCIS as well as microinvasive ductal carcinoma (4). Currently, DCIS accounts for approximately 20% of newly diagnosed breast cancers, with 5–10% of patients with DCIS showing evidence of microinvasion (4, 5). While the incidence of sentinel lymph node metastases in patients with microinvasive ductal carcinoma has been reported up to 20% (2, 6 –10), a lower incidence rate has been reported in the case of patients with pure DCIS (6, 11 –13). Thus, the differentiation between the two disease entities is important to determine whether sentinel lymph node biopsy should be performed or not.

Dynamic contrast-enhanced magnetic resonance imaging (MRI) is being used with conventional imaging technique for preoperative evaluation of malignancy (14, 15). Although several reports have described the MRI findings of pure DCIS (16 –18) or mammographic and ultrasonographic findings of microinvasive ductal carcinoma (2, 19 –23), there have not been well-reported MRI findings of microinvasive ductal carcinoma. In addition, to the best of our knowledge, there have been only a few reports on comparisons of MRI between microinvasive ductal carcinoma and pure DCIS (24, 25). Therefore, the purpose of our study was to evaluate MRI characteristics of microinvasive ductal carcinoma and to compare MRI findings in patients with microinvasive ductal carcinoma and pure DCIS.

Material and Methods

Patients

The institutional review board approved this study and the patient's informed consent requirement was waived. From a retrospective review of the pathologic database of our institution between January 2004 and December 2008, 42 patients who had a histologic diagnosis of microinvasive ductal carcinoma and preoperative MRI were identified. Seven patients were excluded from analysis because excisional biopsy (n = 6) or neoadjuvant chemotherapy (n = 1) was performed in these patients before the MRI studies. Thus, a total of 37 patients with microinvasive ductal carcinoma were included in this study. As a control group, 44 consecutive patients with pure DCIS between January 2008 and December 2008 were selected based on the pathologic database of our institution and were enrolled to the case group, with respect to tumor size. Finally, the MRI findings in 81 patients with surgically confirmed microinvasive ductal carcinoma (n = 37) or pure DCIS (n = 44) were reviewed.

Imaging technique

Bilateral breast MRI was performed with a 1.5 (Signa; GE Healthcare, Milwaukee, WI, USA) or 3.0 (Philips Achieva; Philips Healthcare, Best, The Netherlands) Tesla MRI system. Three-dimensional, fat-suppressed, gradient-echo, contrast material-enhanced, and dynamic images before and seven times after a bolus injection of 0.1 mmol/kg of gadopentetate dimeglumine (Magnevist; Berlex Laboratories, Wayne, NJ, USA) were performed in the sagittal (on 1.5 T; 20 microinvasive ductal carcinoma and 6 pure DCIS) or axial (on 3.0 T; 17 microinvasive ductal carcinoma and 38 pure DCIS) plane. Image acquisition time per one dynamic scan was 60–90 s. Standard subtraction images were obtained by subtracting the precontrast images from the early peak (or serial) postcontrast images on a pixel-by-pixel basis. Reverse subtraction images were obtained by subtracting the last postcontrast images from the early peak postcontrast images.

Interpretation of MR findings

Two radiologists (with more than 15 and 5 years of experience in breast MRI, respectively) retrospectively reviewed the MRI findings without any previous knowledge of the other conventional imaging or pathologic findings. MRI analysis was performed for the MR-detected lesions. Morphologic and kinetic analyses were performed according to the Breast Imaging Reporting and Data System (BI-RADS) MR lexicon (26) by the consensus of the two radiologists. All the morphologic parameters were analyzed on the first or second, and delayed contrast-enhanced MRI. After the lesion type was divided as a mass or a non-mass lesion, the margin, shape, and internal enhancement pattern of the mass-type lesions and the distribution and internal enhancement characteristics of the non-mass-type lesions were analyzed. Among the internal enhancement characteristics of the non-mass lesions, we particularly identified clustered ring enhancement. We defined clustered ring enhancement as a finding in which minute ring enhancements were clustered within the heterogeneously enhancing lesion, which had been described by Tozaki et al. (27). The kinetic parameters were evaluated by manually tracing a region of interest around the most enhancing area on the first contrast-enhanced image. The degree of internal enhancement was analyzed by assessment of signal changes between the precontrast and the first contrast-enhanced images. We defined strong internal enhancement as the more than twice increase in signal intensity from the precontrast measurement within first 60–90 s after contrast administration. The delayed phase enhancement pattern (persistent, plateau, or wash-out) was also analyzed according to the BI-RADS MR lexicon.

Pathologic evaluation

All the pathologic specimens were reviewed by a pathologist with expertise in breast pathology. All the histologic diagnoses were made from surgical specimens and not from core biopsies. The Van Nuys classification system was used for histologic grading (28). DCIS component was classified according to the nuclear grade (non-high grade versus high grade). Grade I (low grade) and Grade II (intermediate grade) were categorized as non-high grade, and Grade III was the high grade. The pathologic results of axillary lymph node surgery, if performed, were also reviewed.

Statistical analysis

Student's t test was used to compare patients' ages and pathologic tumor sizes between patients with microinvasive ductal carcinoma and those with pure DCIS. Qualitative variables between microinvasive ductal carcinoma and pure DCIS were analyzed with χ² test and Fisher's exact test. Student's t test was also used to analyze quantitative variables (lesion sizes on MRI) between the groups. P < 0.05 was considered statistically significant. Statistical analyses were performed using software (SPSS, version 19; SPSS Inc., Chicago, IL, USA).

Results

Patients

The clinical and pathologic characteristics are summarized in Table 1. The patient's age, tumor size, initial manifestation of disease, and surgical type were not significantly different between the two disease entities. However, histologically, high grade tumors were more frequent in microinvasive ductal carcinoma than in DCIS (70.3% vs. 34.1%; P = 0.001). After axillary lymph node surgery including sentinel lymph node biopsy (n = 33) and axillary dissection (n = 4), lymph node metastases were detected in two patients with microinvasive ductal carcinoma (5.4%).
Table 1
Clinicopathologic characteristics of microinvasive ductal carcinoma and DCIS

Microinvasiveductalcarcinoma(n = 37) DCIS(n = 44) Pvalue

Age (years) 48.1 ± 8.1 48.5 ± 9.5 0.823

Pathologic tumor size (cm) 4.3 ± 2.8 3.2 ± 2.3 0.053

Initial manifestation 0.957

Nipple discharge 2 (5.4) 3 (6.8)

Palpable lesion 12 (32.4) 13 (29.5)

MG abnormality 17 (45.9) 22 (50.0)

US abnormality 5 (13.5) 6 (13.6)

PET abnormality 1 (2.7) 0 (0.0)

Surgical type 0.115

Partial mastectomy 28 (75.7) 26 (59.1)

Mastectomy 9 (24.3) 18 (40.9)

Van Nuys classification 0.001

Non-high nuclear grade 11 (29.7) 29 (65.9)

High nuclear grade 26 (70.3) 15 (34.1)

Lymph node metastasis 2 (5.4) 0 (0.0) 0.206

Data are numbers of lesions

Numbers in parentheses are percentages

MG, mammography; PET, positron emission tomography; US, ultrasonography

MRI findings

Total 35 cases of microinvasive ductal carcinoma (94.6%) and 39 cases of DCIS (88.6%) were detected on MRI.

MRI findings of microinvasive ductal carcinoma

On MRI, the lesion types of microinvasive ductal carcinoma were non-mass type in 28 (80.0%) and mass type in seven (20.0%) lesions (Table 2). The mean tumor size of the mass lesions was significantly smaller than that of the non-mass lesions (P = 0.006). The dominant morphologic features were non-mass lesions with segmental distribution and heterogeneous enhancement. Especially, of 24 non-mass lesions with heterogeneous enhancement, 16 lesions revealed clustered ring enhancement (Fig. 1). All seven mass lesions of microinvasive ductal carcinoma also showed heterogeneous enhancement (Fig. 2). The dominant kinetic characteristics revealed strong enhancement in the early phase and wash-out from peak enhancement in the delayed phase (Table 3). These kinetic characteristics such as enhancement degree or kinetic pattern had no significant differences between the two lesion types on MRI (enhancement degree, P = 0.594; kinetic pattern, P = 0.311).
Table 2
Morphologic characteristics of microinvasive ductal carcinoma, DCIS, and high grade DCIS on MRI

Microinvasive ductalcarcinoma (n = 35) DCIS (n = 39) High gradeDCIS (n = 15) P value* P value^†

MR-measured tumor size (cm) 4.0 ± 2.2 2.8 ± 2.0 3.5 ± 2.0 0.015 0.404

Lesion type 0.411 1.000

Non-mass 28 (80.0) 28 (71.8) 12 (80.0)

Mass 7 (20.0) 11 (28.2) 3 (20.0)

Non-mass lesions

MR-measured tumor size (cm) 4.5 ± 2.1 1.5 ± 1.0 3.9 ± 1.9 0.041 0.383

Distribution 0.023 0.035

Segmental 27 (77.1) 20 (71.5) 8 (66.6)

Linear 1 (2.9) 2 (7.1) 2 (16.7)

Regional 0 (0.0) 6 (21.4) 2 (16.7)

E characteristics 0.669 1.000

Homogeneous 4 (14.3) 2 (7.1) 1 (8.3)

Heterogeneous 24 (85.7) 26 (92.9) 11 (91.7)

Clustered ring 16 (57.1) 8 (28.6) 2 (16.7) 0.006 0.035

Mass lesions

MR-measured tumor size (cm) 2.1 ± 1.2 3.4 ± 2.0 2.0 ± 1.4 0.251 0.909

Shape 0.066 1.000

Oval 0 (0.0) 5 (45.4) 0 (0.0)

Lobulated 1 (14.3) 2 (18.2) 1 (33.3)

Irregular 6 (85.7) 4 (36.4) 2 (66.7)

Margin 0.022 0.033

Smooth 1 (14.3) 3 (27.3) 0 (0.0)

Irregular 1 (14.3) 7 (63.6) 3 (100.0)

Spiculated 5 (71.4) 1 (9.1) 0 (0.0)

E pattern 1.000 0.300

Homogeneous 0 (0.0) 1 (9.1) 1 (33.3)

Heterogeneous 7 (100.0) 10 (90.9) 2 (66.7)

The statistical significances of differences in imaging characteristics between patients with microinvasive ductal carcinoma and those with DCIS were evaluated

^†The statistical significances of differences in imaging characteristics between patients with microinvasive ductal carcinoma and those with high grade DCIS were evaluated

Data are numbers of lesions

Numbers in parentheses are percentages

E, enhancement

Table 3
Kinetic characteristics of microinvasive ductal carcinoma, DCIS, and high grade DCIS on MRI

Microinvasive ductalcarcinoma (n = 35) DCIS(n = 39) High gradeDCIS (n = 15) P value P value^†

E degree 0.004 0.021

Mild 9 (25.7) 23 (59.0) 9 (60.0)

Strong 26 (74.3) 16 (41.0) 6 (40.0)

Kinetic pattern 0.001 0.012

Persistent 6 (17.2) 16 (41.0) 5 (33.3)

Plateau 11 (31.4) 18 (46.2) 9 (60.0)

Wash-out 18 (51.4) 5 (12.8) 1 (6.7)

The statistical significances of differences in imaging characteristics between patients with microinvasive ductal carcinoma and those with DCIS were evaluated

^†The statistical significances of differences in imaging characteristics between patients with microinvasive ductal carcinoma and those with high grade DCIS were evaluated

Data are numbers of lesions

Numbers in parentheses are percentages

E, enhancement

Fig. 1
A 46-year-old woman with MRI findings of microinvasive ductal carcinoma in right breast. (a) Sagittal first contrast-enhanced T1-weighted MRI shows non-mass lesion with segmental distribution and heterogeneous enhancement. (b) Transverse delayed contrast-enhanced T1-weighted MRI shows heterogeneous enhancements with clustered ring enhancements (arrows)

Fig. 2
A 49-year-old woman with MRI findings of microinvasive ductal carcinoma in left breast. Transverse delayed contrast-enhanced T1-weighted MRI shows an irregular mass with heterogeneous enhancement

Comparison of MRI findings with DCIS

Twenty-eight lesions (80.0%) of microinvasive ductal carcinoma and another 28 lesions (71.8%) of DCIS were observed as non-mass lesions on MRI (P = 0.411) (Table 2). For the non-mass lesions, the mean tumor size in microinvasive ductal carcinoma was significantly larger than that in DCIS (P = 0.041). However, there was no significant difference in the mean tumor size of the mass lesions between microinvasive ductal carcinoma and DCIS (P = 0.251).

According to the morphologic analyses for the non-mass lesions, the dominant MRI findings of microinvasive ductal carcinoma and DCIS were segmental distribution and heterogeneous enhancement (Figs. 1 and 3). However, all six non-mass lesions with regional distribution were found to be DCIS (15.4%; P = 0.022). Clustered ring enhancement was significantly more frequent in microinvasive ductal carcinoma than in DCIS (57.1%). On MRI, seven lesions (20.0%) of microinvasive ductal carcinoma and 11 lesions (28.2%) of DCIS were demonstrated as mass lesions (P = 0.411) (Table 2). According to the morphologic analyses for the mass lesions, spiculated margins were significantly more frequent in microinvasive ductal carcinoma than in DCIS (P = 0.022).
Fig. 3
A 53-year-old woman with MRI findings of high grade DCIS in left breast. (a) Sagittal first contrast-enhanced T1-weighted MRI shows non-mass lesion with segmental distribution and heterogeneous enhancement. (b) Transverse delayed contrast-enhanced T1-weighted MRI shows heterogeneous enhancement without clustered ring enhancement

According to the kinetic analyses, microinvasive ductal carcinoma lesions exhibited significantly stronger enhancement in the early phase than did DCIS lesions (74.3% vs. 41.0%; P = 0.004) (Table 3). A significantly higher incidence of wash-out pattern in the delayed phase was found in the case of microinvasive ductal carcinoma than that of DCIS (51.4% vs. 12.8%; P = 0.001). These kinetic characteristics had no significant differences between non-high grade DCIS and high grade DCIS on MRI (enhancement degree, P = 0.918; kinetic pattern, P = 0.390).

Comparison of MRI findings with high grade DCIS

Twenty-eight lesions (80.0%) of microinvasive ductal carcinoma and 12 lesions (80.0%) of high grade DCIS were observed as non-mass lesions on MRI (P = 1.000) (Table 2).

In the case of microinvasive ductal carcinoma, the spiculated margin of the mass-type lesion (P = 0.033), the segmental distribution (P = 0.035) and clustered ring enhancement (P = 0.035) of the non-mass-type lesion, and the enhancement kinetics showing strong initial enhancement (P = 0.021) with subsequent wash-out (P = 0.012) were significantly more frequent than those of high grade DCIS (Tables 2 and 3).

Discussion

In this study, the dominant MRI findings of microinvasive ductal carcinoma were non-mass-type lesions, segmental distribution, and heterogeneous or clustered ring enhancement. The most common kinetic pattern of microinvasive ductal carcinoma lesions included strong initial enhancement with a wash-out curve. The MRI of microinvasive ductal carcinoma demonstrated more suspicious morphologic and kinetic characteristics when compared with DCIS. Furthermore, strong enhancement on the early phase and clustered ring enhancement on the delayed phase were also distinctive characteristics of microinvasion on MRI.

In our study, we found that the dominant lesion type of microinvasive ductal carcinoma was a non-mass type (80.0%). In addition, we also found that mass lesion type was a characteristic feature of microinvasive ductal carcinoma lesions with relatively small tumor sizes (P = 0.006). Our observation supported the findings of a previous study regarding microinvasive ductal carcinomas (mean size, 2.1 cm; range, 0.9–6.5 cm) (23), which reported that the smaller microinvasive ductal carcinoma lesions had a tendency to present as a mass on conventional images; moreover, another previous study by Liu et al.* (29), which reported that microinvasive ductal carcinoma lesions with relatively large tumor sizes (mean size, 4.3 cm; range, 0.7–12.0 cm) were more frequently presented as non-mass lesions (77.8%) on MRI. These findings can explain that the large percentage of our microinvasive ductal carcinoma cases was found to be non-mass lesions on MRI.

We also found that the mean tumor size measured by MRI was significantly larger in microinvasive ductal carcinoma than in DCIS (P = 0.015), however, that was not significantly different between microinvasive ductal carcinoma and high grade DCIS groups (P = 0.404). Meanwhile, the mean pathologic tumor size of microinvasive ductal carcinoma lesions was slightly larger, but not significantly different from that of DCIS lesions (P = 0.053). These findings are in agreement with results reported by Viehweg et al. (24) and Neubauer et al. (30), who suggested that low nuclear grade of DCIS was correlated with the reducing sensitivity for the tumor detection and the under-estimation of the tumor size by MRI.

According to the morphologic analyses for the mass lesions, we observed that the margins showed a significant difference between the two groups (P = 0.022) (Table 2). The majority of microinvasive ductal carcinoma cases showing mass-type enhancements had irregular shapes (85.7%) with spiculated margins (71.4%). However, DCIS lesions showing mass-type enhancements predominantly had irregular margins (63.6%) with the variable shapes across the nuclear grades, which were in relative agreement with the imaging findings in previous reports (18, 31). Thus, mass-type lesions of microinvasive ductal carcinoma showed more suspicious morphologic characteristics on MRI than did those of DCIS.

In our study, according to the BI-RADS MR lexicon (Figs. 1 and 3), the dominant MRI findings in microinvasive ductal carcinoma and DCIS were non-mass lesions with segmental distribution and heterogeneous enhancement. These findings were concordant with the previously reported findings (16, 18, 29, 30, 32). However, we found that clustered ring enhancement was significantly more frequent in non-mass lesions of microinvasive ductal carcinoma than in those of DCIS (57.1% vs. 21.4%; P = 0.006).

Clustered ring enhancement was presented in 16 cases of microinvasive ductal carcinoma (57.1%) and six cases of DCIS (25.0% of non-high grade DCIS and 16.7% of high grade DCIS) in our study. We defined clustered ring enhancement as a finding in which minute ring enhancements are clustered within the heterogeneously enhancing lesion (27) and evaluated on the delayed postcontrast images. Tozaki et al. reported that the imaging finding with the highest positive predictive value for malignancy was clustered ring enhancement in non-mass lesions (27, 33). According to their report, the histologic characteristics corresponding to clustered ring enhancement were crowded intraductal carcinoma (33). Thus, clustered ring enhancement reflects the enhancement of ductal carcinoma and the periductal space.

We found that the kinetic characteristics of microinvasive ductal carcinoma lesions were significantly different with those of DCIS lesions (Table 3). In the early phase of dynamic contrast-enhanced MRI, microinvasive ductal carcinoma lesions exhibited significantly stronger enhancement than did DCIS lesions (74.3% vs. 41.0%; P = 0.004). In the delayed phase, moreover, wash-out pattern was significantly more frequent in microinvasive ductal carcinoma than in DCIS (51.4% vs. 12.8%; P = 0.001). However, there was no significant differences in enhancement kinetic properties across the nuclear grades of DCIS (enhancement degree, P = 0.918; kinetic pattern, P = 0.390), which was in relative agreement with the imaging findings in previous reports (18, 24, 34). Therefore, microinvasive ductal carcinoma lesions showed more suspicious kinetic characteristics than did pure DCIS lesions regardless of the lesion types on MRI (enhancement degree, P = 0.594; kinetic pattern, P = 0.311).

In our study, histologically high grade tumors were more frequent in microinvasive ductal carcinoma than DCIS (71.4% vs. 38.5%; P = 0.004). This finding was similar to the data described in the previous reports (6, 23, 29, 35). According to the previous reports regarding microinvasive ductal carcinoma, the incidence of high grade tumors ranged from 46.3% to 81.8%. In this study, we analyzed the MRI characteristics of microinvasive ductal carcinoma and compared them with the imaging findings of all pure DCIS as well as of high grade DCIS (Tables 2 and 3). Between these two sets of analyses, the results were comparatively consistent across the two analyses, excepting the significance level for the mass margin. Thus, even though the incidence of high grade tumors in microinvasive ductal carcinoma was greater than that in DCIS; we found reliable differences in MRI characteristics between microinvasive ductal carcinoma and DCIS.

We found that two cases (5.7%) had lymph node metastases (one macrometastasis and one micrometastasis) among 35 microinvasive ductal carcinoma lesions, which had undergone axillary surgery. This incidence of our study was similar to the data described in the previous literatures (6, 11, 23).

There are several limitations in our study. First, we did not correlate the MRI findings with the mammographic findings, although mammography is the basic imaging modality for the evaluation of patients with breast abnormalities. Second, we used two protocols for dynamic MRI depending on the two different MR systems. These could influence the interpretation of MRI, although the techniques were similar in both the protocols. Third, while Tozaki et al. decided the presence of clustered ring enhancement on MRI obtained during the third phase (27, 33), we evaluated the presence of clustered ring enhancement on the delayed postcontrast images. However, we evaluated the comparative analyses for the clustered ring enhancements between microinvasive ductal carcinoma and DCIS lesions. Thus, this might not be considered as a critical limitation of our study. Forth, we performed the analyses with a small number of study populations. Lastly, the analyses were performed retrospectively and by two radiologists in consensus. A prospective study with more populations would be desirable to verify our results.

In conclusion, non-mass lesions with segmental distribution, heterogeneous enhancement, and strong initial enhancement with a wash-out curve were the dominant MRI findings of microinvasive ductal carcinoma. Despite the resulting limitation in numbers, according to the BI-RADS MR lexicon, microinvasive ductal carcinoma had more suspicious morphologic and kinetic characteristics than did DCIS. For the non-mass lesions, clustered ring enhancement was also a characteristic finding of microinvasion on MRI. A combination of BI-RADS MR lexicon and clustered ring enhancement would be helpful to predict microinvasion especially in patients with high grade DCIS and to determine the treatment plan including sentinel lymph node biopsy.

	Microinvasiveductalcarcinoma(n = 37)	DCIS(n = 44)	Pvalue
Age (years)	48.1 ± 8.1	48.5 ± 9.5	0.823
Pathologic tumor size (cm)	4.3 ± 2.8	3.2 ± 2.3	0.053
Initial manifestation			0.957
Nipple discharge	2 (5.4)	3 (6.8)
Palpable lesion	12 (32.4)	13 (29.5)
MG abnormality	17 (45.9)	22 (50.0)
US abnormality	5 (13.5)	6 (13.6)
PET abnormality	1 (2.7)	0 (0.0)
Surgical type			0.115
Partial mastectomy	28 (75.7)	26 (59.1)
Mastectomy	9 (24.3)	18 (40.9)
Van Nuys classification			0.001
Non-high nuclear grade	11 (29.7)	29 (65.9)
High nuclear grade	26 (70.3)	15 (34.1)
Lymph node metastasis	2 (5.4)	0 (0.0)	0.206

	Microinvasive ductalcarcinoma (n = 35)	DCIS (n = 39)	High gradeDCIS (n = 15)	P value*	P value^†
MR-measured tumor size (cm)	4.0 ± 2.2	2.8 ± 2.0	3.5 ± 2.0	0.015	0.404
Lesion type				0.411	1.000
Non-mass	28 (80.0)	28 (71.8)	12 (80.0)
Mass	7 (20.0)	11 (28.2)	3 (20.0)
Non-mass lesions
MR-measured tumor size (cm)	4.5 ± 2.1	1.5 ± 1.0	3.9 ± 1.9	0.041	0.383
Distribution				0.023	0.035
Segmental	27 (77.1)	20 (71.5)	8 (66.6)
Linear	1 (2.9)	2 (7.1)	2 (16.7)
Regional	0 (0.0)	6 (21.4)	2 (16.7)
E characteristics				0.669	1.000
Homogeneous	4 (14.3)	2 (7.1)	1 (8.3)
Heterogeneous	24 (85.7)	26 (92.9)	11 (91.7)
Clustered ring	16 (57.1)	8 (28.6)	2 (16.7)	0.006	0.035
Mass lesions
MR-measured tumor size (cm)	2.1 ± 1.2	3.4 ± 2.0	2.0 ± 1.4	0.251	0.909
Shape				0.066	1.000
Oval	0 (0.0)	5 (45.4)	0 (0.0)
Lobulated	1 (14.3)	2 (18.2)	1 (33.3)
Irregular	6 (85.7)	4 (36.4)	2 (66.7)
Margin				0.022	0.033
Smooth	1 (14.3)	3 (27.3)	0 (0.0)
Irregular	1 (14.3)	7 (63.6)	3 (100.0)
Spiculated	5 (71.4)	1 (9.1)	0 (0.0)
E pattern				1.000	0.300
Homogeneous	0 (0.0)	1 (9.1)	1 (33.3)
Heterogeneous	7 (100.0)	10 (90.9)	2 (66.7)

	Microinvasive ductalcarcinoma (n = 35)	DCIS(n = 39)	High gradeDCIS (n = 15)	P value*	P value^†
E degree				0.004	0.021
Mild	9 (25.7)	23 (59.0)	9 (60.0)
Strong	26 (74.3)	16 (41.0)	6 (40.0)
Kinetic pattern				0.001	0.012
Persistent	6 (17.2)	16 (41.0)	5 (33.3)
Plateau	11 (31.4)	18 (46.2)	9 (60.0)
Wash-out	18 (51.4)	5 (12.8)	1 (6.7)

Footnotes

Conflict of interest: None.

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