Can we apply the MRI BI-RADS lexicon morphology descriptors on contrast-enhanced spectral mammography?

Abstract

Objective:: To assess the feasibility of using the MRI breast imaging reporting and data system (BI-RADS) lexicon morphology descriptors to characterize enhancing breast lesions identified on contrast-enhanced spectral mammography (CESM).

Methods:: The study is a retrospective analysis of the morphology descriptors of 261 enhancing breast lesions identified on CESM in 239 patients. We presented the morphological categorization of the included lesions into focus, mass and non-mass. Further classifications included (1) the multiplicity for "focus" category, (2) the shape, margin and internal enhancement for "mass" category and (3) the distribution and internal enhancement for "non-mass" category. Each morphology descriptor was evaluated individually (irrespective of all other descriptors) by calculating its sensitivity, specificity, positive-predictive value (PPV) and negative-predictive value (NPV) and likelihood ratios (LRs).

Results:: The study included 68/261 (26.1%) benign lesions and 193/261 (73.9%) malignant lesions. Intensely enhancing foci, whether single (7/12, 58.3%) or multiple (2/12, 16.7%), were malignant. Descriptors of "irregular"-shape (PPV: 92.4%) and "non-circumscribed" margin (odds ratio: 55.2, LR positive: 4.77; p-value: <0.001) were more compatible with malignancy. Internal mass enhancement patterns showed a very low specificity (58.0%) and NPV (40.0%). Non-mass enhancement (NME) was detected in 81/261 lesions. Asymmetrical NME in 81% (n = 52/81) lesions was malignant lesions and internal enhancement patterns indicative of malignancy were the heterogeneous and clumped ones.

Conclusion:: We can apply the MRI morphology descriptors to characterize lesions on CESM, but with few expectations. In many situations, irregular-shaped, non-circumscribed masses and NME with focal, ductal or segmental distribution and heterogeneous or clumped enhancement are the most suggestive descriptors of malignant pathologies.

Advances in knowledge:: (1) The MRI BI-RADS lexicon morphology descriptors can be applied in the characterization of enhancing lesions on CESM with a few exceptions. (2) Multiple bilateral intensely enhancing foci should not be included under the normal background parenchymal enhancement unless they are proved to be benign by biopsy. (3) Mass lesion features that indicated malignancy were irregular-shaped, spiculated and irregular margins and heterogeneous internal enhancement patterns. The rim enhancement pattern should not be considered as a descriptor of malignant lesions unless CESM is coupled with an ultrasound examination.

Figure 1.

Different cases demonstrating examples of enhancing foci on contrast-enhanced spectral mammography: (a) a single benign focus (arrow), (b) multiple diffuse and bilateral foci of adenosis, (c) a single malignant focus which proved to be invasive ductal carcinoma (IDC) (arrow) and (d) multiple enhancing foci of mixed IDC and invasive lobular carcinoma (ILC).

Figure 2.

Contrast-enhanced spectral mammography images in three different cases showing shape patterns of enhancing masses: (a) rounded and (b) oval shape patterns both consistent with fibroadenoma; and (c) an irregular mass shape for invasive ductal carcinomas (IDCs).

Figure 3.

Mass margin assessment on contrast-enhanced spectral mammography images in three different cases: (a) fibroadenoma with a circumscribed margin; (b, c) non-circumscribed margin in an irregular (b) or spiculated (c) form in two cases of invasive ductal carcinoma (IDC).

Figure 4.

Five different examples of rim enhancement pattern on contrast-enhanced spectral mammography, four of which were benign. (a) A thin uniform mural enhancement can be noted in an infected cyst (arrows); (b, c) thick rim enhancement of the uniform outline in granulomatous mastitis and post-operative infected seroma (arrows). (d, e) A dilemma presented with the non-uniform irregular thick rim enhancement noted in the “malignant” invasive ductal carcinoma (IDC) (d) and the “benign” abscess cavity (e) (arrows).

Figure 5.

Example patterns of internal enhancement of masses on contrast-enhanced spectral mammography. (a) A craniocaudal view showing fibroadenoma with homogeneous enhancement; (b) an enhancing circumscribed mass with dark non-enhancing internal septations (arrow) characteristic of fibroadenomas; and (c) a mediolateral oblique view showing an invasive ductal carcinoma (IDC) with heterogeneous internal enhancement pattern (arrows).

Figure 6.

Non-mass enhancement (NME) patterns in contrast-enhanced spectral mammography images. (a–c) Three cases of invasive ductal carcinomas (IDCs) that demonstrate examples of homogeneous (a), heterogonous (b) and clumped (c) patterns of NME (arrows). (d) The clustered ring NME pattern in most of the situations describing the inflammatory process as in granulomatous (granulom.) mastitis (arrows).

Figure 7.

Mediolateral oblique views of six different cases showing variable distributions of non-mass enhancement (NME) patterns on contrast-enhanced spectral mammography images. (a–e) Invasive ductal carcinomas (IDCs) presenting focal (a), linear (b), segmental (c), regional (d) and multiple region (e) patterns (arrows). (f) A diffuse NME pattern with adenosis (arrows).