Magnetic resonance mammography of invasive lobular versus ductal carcinoma: systematic comparison of 811 patients reveals high diagnostic accuracy irrespective of typing

Correlations of Imaging and Therapy in Breast Cancer Based on Molecular Patterns: An Important Issue in the Diagnosis of Breast Cancer

Breast cancer is a global health issue affecting countries worldwide, imposing a significant economic burden due to expensive treatments and medical procedures, given the increasing incidence. In this review, our focus is on exploring the distinct imaging features of known molecular subtypes of breast cancer, underlining correlations observed in clinical practice and reported in recent studies. The imaging investigations used for assessment include screening modalities such as mammography and ultrasonography, as well as more complex investigations like MRI, which offers high sensitivity for loco-regional evaluation, and PET, which determines tumor metabolic activity using radioactive tracers. The purpose of this review is to provide a better understanding as well as a revision of the imaging differences exhibited by the molecular subtypes and histopathological types of breast cancer.

Multiparametric MRI-based radiomic nomogram for predicting HER-2 2+ status of breast cancer

Objective

To explore the application of multiparametric MRI-based radiomic nomogram for assessing HER-2 2+ status of breast cancer (BC).

Methods

Patients with pathology-proven HER-2 2+ invasive BC, who underwent preoperative MRI were divided into training (72 patients, 21 HER-2-positive and 51 HER-2-negative) and validation (32 patients, 9 HER-2-positive and 23 HER-2-negative) sets by randomization. All were classified as HER-2 2+ FISH-positive (HER-2-positive) or -negative (HER-2-negative) according to IHC and FISH. The 3D VOI was drawn on MR images by two radiologists. ADC, T2WI, and DCE images were analyzed separately to extract features (n = 1906). L1 regularization, F-test, and other methods were used to reduce dimensionality. Binary radiomics prediction models using features from single or combined imaging sequences were constructed using logistic regression (LR) classifier then and validated on a validation dataset. To build a radiomics nomogram, multivariate LR analysis was conducted to identify independent indicators. An evaluation of the model's predictive efficacy was made using AUC.

Results

On the basis of combined ADC, T2WI, and DCE images, ten radiomic features were extracted following feature dimensionality reduction. There was superior diagnostic efficiency of radiomic signature using all three sequences compared to either one or two sequences (AUC for training group: 0.883; AUC for validation group: 0.816). Based on multivariate LR analysis, radiomic signature and peritumoral edema were independent predictors for identifying HER-2 2 +. In both training and validation datasets, nomograms combining peritumoral edema and radiomics signature demonstrated an effective discrimination (AUCs were respectively 0.966 and 0. 884).

Conclusion

The nomogram that incorporated peritumoral edema and multiparametric MRI-based radiomic signature can be used to effectively predict the HER-2 2+ status of BC.

Contrast-enhanced breast imaging: Current status and future challenges

BACKGROUND

Contrast-enhanced breast MRI and recently also contrast-enhanced mammography (CEM) are available for breast imaging. The aim of the current overview is to explore existing evidence and ongoing challenges of contrast-enhanced breast imaging.

METHODS

This narrative provides an introduction to the contrast-enhanced breast imaging modalities breast MRI and CEM. Underlying principle, techniques and BI-RADS reporting of both techniques are described and compared, and the following indications and ongoing challenges are discussed: problem-solving, high-risk screening, supplemental screening in women with extremely dense breast tissue, breast implants, neoadjuvant systemic therapy (NST) response monitoring, MRI-guided and CEM- guided biopsy.

RESULTS

Technique and reporting for breast MRI are standardised, for the newer CEM standardisation is in progress. Similarly, compared to other modalities, breast MRI is well established as superior for problem-solving, screening women at high risk, screening women with extremely dense breast tissue or with implants; and for monitoring response to NST. Furthermore, MRI-guided biopsy is a reliable technique with low long-term false negative rates. For CEM, data is as yet either absent or limited, but existing results in these settings are promising.

CONCLUSION

Contrast-enhanced breast imaging achieves highest diagnostic performance and should be considered essential. Of the two contrast-enhanced modalities, evidence of breast MRI superiority is ample, and preliminary results on CEM are promising, yet CEM warrants further study.

Non-enhancing malignant lesions of the breast: A case report and review of literature

Due to the elusive nature of invasive lobular carcinoma, mammography, ultrasound, and magnetic resonance imaging have their limitations in early detection. A 67-year-old woman presented for mammography and found retraction of breast parenchyma of the right breast. Magnetic resonance imaging and contrast mammography showed no contrast uptake in the region in question. Magnetic resonance imaging and ultrasound were found to be superior for the detection of invasive lobular carcinoma, with a sensitivity of more than 90%. On ultrasound examination, invasive lobular carcinoma may occur only with posterior acoustic shadowing. On breast magnetic resonance imaging, it is commonly described as an irregular mass and less commonly as non-mass enhancement. An additional advantage of magnetic resonance imaging is the higher detection rate of multifocal, multicentric, and contralateral breast lesions. The reason for no contrast enhancement in this particular tumor before neoadjuvant chemotherapy followed by enhancement after neoadjuvant chemotherapy is most likely at the molecular and histologic level and requires further investigation in similar cases.

Diagnostically Challenging Subtypes of Invasive Lobular Carcinomas: How to Avoid Potential Diagnostic Pitfalls

Invasive lobular carcinoma is the most common special breast carcinoma subtype, with unique morphological (discohesive cells, single-cell files, targetoid pattern) and immunohistochemical (loss of E-cadherin and β-catenin staining) features. Moreover, ILC displays a poor response to neoadjuvant therapy, a different metastatic pattern compared to invasive breast carcinoma of no special type, as well as unique molecular characteristics. In addition to the classic variant of invasive lobular carcinoma, several other well-recognized variants exist, including classic, alveolar, tubulolobular, solid, pleomorphic, signet-ring, and mixed. Furthermore, three novel variants of invasive lobular carcinoma, i.e., with extracellular mucin production, papillary features, and tubular elements, have been described during the last decade. We herewith focus on the unique morphological and immunohistochemical characteristics of these novel varieties of invasive lobular carcinoma, as well as differential diagnostic considerations and potential diagnostic pitfalls, especially when dealing with biopsy specimens.

Presence of peritumoral edema on T2w MRI: a poor non-invasive prognostic marker in breast cancer patients

Background

The purpose of the study was to assess the correlation between peritumoral edema (PE) seen on magnetic resonance imaging (MRI) in breast cancer and the established pathological prognostic factors like tumor histology and molecular subtype, grade, Ki67 index, lymphovascular invasion (LVI) and nodal stage. The breast MRI and pathological data of post-surgery specimen of 126 breast cancer patients over a period of 18 months were retrospectively studied. Those who received neoadjuvant therapy, had non-invasive, locally advanced, inflammatory and bilateral breast cancers were excluded. Patients were divided into two groups based on finding of peritumoral edema on T2w MRI images: Group A with PE (n = 88) and Group B without PE (n = 38). Pathological results for the two groups were analyzed and compared using Chi square test. p values of < .05 were considered as significant.

Results

Statistically significant correlation was found between the PE and molecular subtype (p value of < .01), high grade (p value of .001) and High Ki-67 index (p value of .001). No significant correlation was present for the histological type and LVI pathological nodal stage (pN).

Conclusions

We concluded that presence of PE on MRI is associated with poor pathological prognostic factors in breast cancer. It can serve as an additional non-invasive marker to assess prognosis in breast cancer patients especially in those receiving neoadjuvant therapy where the whole tumor may not be available for pathological analysis post-therapy.

Multimodality imaging in lobular breast cancer: Differences in mammography, ultrasound, and MRI in the assessment of local tumor extent and correlation with molecular characteristics

Introduction

Invasive lobular breast cancer (ILC) is a diagnostic challenge due to the diversity of morphological features. The objective of the study was to investigate the presentation and local extent of ILC using various imaging techniques and to assess the correlation between imaging and molecular profile.

Materials and methods

We reviewed 162 consecutive patients with ILC found on vacuum-assisted biopsy, who underwent evaluation of the lesion morphology and extent using ultrasound (US), mammography (MMG), and magnetic resonance imaging (MRI). Radiographic features were compared with ILC intrinsic subtype based on the expression of Ki-67 and estrogen, progesterone, and HER2 receptors.

Results

A total of 113 mass lesions and 49 non-mass enhancements (NMEs) were found in MRI. Masses were typically irregular and spiculated, showing heterogeneous contrast enhancement, diffusion restriction, and type III enhancement curve. NMEs presented mainly as the area of focal or multiregional distribution with heterogeneous or clumped contrast enhancement, diffusion restriction, and type III enhancement curve. Lesion extent significantly varied between MRI and MMG/ultrasonography (USG) (P < 0.001) but did not differ between MGF and ultrasonography (USG). The larger the ILC, the higher the disproportion when lesion extent in MRI was compared with MMG (P < 0.001) and ultrasonography (USG) (P < 0.001). In the study group, there were 97 cases of luminal A subtype (59.9%), 54 cases of luminal B HER2− (33.3%), nine cases of luminal B HER2+ (5.5%), and two cases of triple negative (1.2%). The HER2 type was not found in the study group. We did not observe any significant correlation between molecular profile and imaging.

Conclusion

MRI is the most effective technique for the assessment of ILC local extent, which is important for optimal treatment planning. Further studies are needed to investigate if the intrinsic subtype of ILC can be predicted by imaging features on MRI.

Special Histologic Type and Rare Breast Tumors - Diagnostic Review and Clinico-Pathological Implications

Breast cancer is the most common malignant tumor in females. While most carcinomas are categorized as invasive carcinoma, no special type (NST), a diverse group of tumors with distinct pathologic and clinical features is also recognized, ranging in incidence from relatively more common to rare. So-called "special histologic type" tumors display more than 90% of a specific, distinctive histologic pattern, while a spectrum of tumors more often encountered in the salivary gland may also arise in the breast. Metaplastic carcinomas can present diagnostic challenges. Some uncommon tumors harbor pathognomonic genetic alterations. This article provides an overview of the key diagnostic points and differential diagnoses for this group of disparate lesions, as well as the salient clinical characteristics of each entity.

The Impact of Tumor Edema on T2-Weighted 3T-MRI Invasive Breast Cancer Histological Characterization: A Pilot Radiomics Study

Simple Summary

Breast cancer is the most common cancer in women worldwide. Currently the use of MR is mandatory in staging phase. The standard protocol includes T2-weighted sequences for morphology and signal analysis, T1-weighted images for adding information (i.e., ematic or adipous components), diffusion-weighted sequences which provide information on tissue cellularity, and dynamic post-contrast sequences useful for detecting and locating lesions. Although not considered among the main prognostic factors in current guidelines, tumor-associated edema provides useful information on tumor aggressiveness, and has been shown to be associated with the main histological tumor characteristics. With this work, entitled “The Impact of Tumor Edema on T2-weighted 3T-MRI Invasive Breast Cancer Histological Characterization: a Pilot Radiomics Study”, we want to demonstrate that radiomics edema, based on algorithms that allow the extraction of imaging features not visible to the human eye, can further increase the accuracy in the prediction of histological factors compared to the use of traditional information only.

Abstract

Background: to evaluate the contribution of edema associated with histological features to the prediction of breast cancer (BC) prognosis using T2-weighted MRI radiomics. Methods: 160 patients who underwent staging 3T-MRI from January 2015 to January 2019, with 164 histologically proven invasive BC lesions, were retrospectively reviewed. Patient data (age, menopausal status, family history, hormone therapy), tumor MRI-features (location, margins, enhancement) and histological features (histological type, grading, ER, PgR, HER2, Ki-67 index) were collected. Of the 160 MRI exams, 120 were considered eligible, corresponding to 127 lesions. T2-MRI were used to identify edema, which was classified in four groups: peritumoral, pre-pectoral, subcutaneous, or diffuse. A semi-automatic segmentation of the edema was performed for each lesion, using 3D Slicer open-source software. Main radiomics features were extracted and selected using a wrapper selection method. A Random Forest type classifier was trained to measure the performance of predicting histological factors using semantic features (patient data and MRI features) alone and semantic features associated with edema radiomics features. Results: edema was absent in 37 lesions and present in 127 (62 peritumoral, 26 pre-pectoral, 16 subcutaneous, 23 diffuse). The AUC-classifier obtained by associating edema radiomics with semantic features was always higher compared to the AUC-classifier obtained from semantic features alone, for all five histological classes prediction (0.645 vs. 0.520 for histological type, 0.789 vs. 0.590 for grading, 0.487 vs. 0.466 for ER, 0.659 vs. 0.546 for PgR, and 0.62 vs. 0.573 for Ki67). Conclusions: radiomic features extracted from tumor edema contribute significantly to predicting tumor histology, increasing the accuracy obtained from the combination of patient clinical characteristics and breast imaging data.

Magnetic Resonance Imaging Features in Different Types of Invasive Breast Cancer: A Systematic Review of the Literature

Breast cancer is the most common malignancy affecting women worldwide, and early diagnosis of breast cancer is the key to its successful and effective treatment. Traditional imaging techniques such as mammography and ultrasound are used to detect and configure breast abnormalities; unfortunately, these modalities have low sensitivity and specificity, particularly in young patients with dense breast tissue, breast implants, or post-surgical scar/architecture distortions. Therefore, breast magnetic resonance imaging (MRI) has been superior in the characterization and detection of breast cancer, especially that with invasive features. This review article explores the importance of breast MRI in the early detection of invasive breast cancer versus traditional tools, including mammography and ultrasound, while also analyzing the use of MRI as a screening tool for high-risk women. We will also discuss the different MRI features for invasive ductal carcinoma and lobular carcinoma and the role of breast MRI in the detection of ductal carcinoma in situ with a focus on the utilization of new techniques, including MR spectroscopy and diffusion-weighted imaging.

Differences in degree of lesion enhancement on CEM between ILC and IDC

Objective:

To investigate differences in the degree of enhancement on contrast-enhanced mammography (CEM) between patients with invasive lobular (ILC) and infiltrating ductal carcinoma (IDC) not otherwise specified.

Methods and materials:

Between 2010 and 2017, all patients diagnosed with ILC and who underwent CEM were included for this dual center study. Twenty-two patients with IDC, matched by size, were identified for comparison. Three independent readers, blinded for histopathology results, re-evaluated all CEM exams to determine degree of lesion enhancement according to a previously defined scoring scale ranging from minimal to strong enhancement. Interobserver agreement among the three readers was calculated by quadratic weighted κ coefficient.

Results:

44 patients were included: 22 patients with ILC and 22 patients with IDC. There were no significant differences in age, mean tumor size, tumor grade or receptor status between the two subgroups. Degree of lesion enhancement on CEM was more often considered weak in case of ILC compared to IDC according to two out of three readers (31.8% vs 4.5 %, p = 0.045 and 22.7 vs 4.5 %, p = 0.185). All other lesions showed moderate or strong enhancement. Interobserver agreement between the three independent readers was good (κ = 0.72).

Conclusion:

In patients with ILC, degree of lesion enhancement on CEM appears to be more often weak than in infiltrating ductal carcinoma not otherwise specified. Radiologists should be aware that weakly enhancing lesions may in fact be malignant and particularly invasive lobular cancers.

Advances in knowledge:

Three independent readers evaluated 44 CEM cases with ILC or IDC. Degree of lesion enhancement seems more often weak in case of ILC. Radiologists should be aware of ILC in case of weak CEM enhancement.

Quantitative evaluation of contrast agent uptake in standard fat-suppressed dynamic contrast-enhanced MRI examinations of the breast

PURPOSE

To propose a method to quantify T1 and contrast agent uptake in breast dynamic contrast-enhanced (DCE) examinations undertaken with standard clinical fat-suppressed MRI sequences and to demonstrate the proposed approach by comparing the enhancement characteristics of lobular and ductal carcinomas.

METHODS

A standard fat-suppressed DCE of the breast was performed at 1.5 T (Siemens Aera), followed by the acquisition of a proton density (PD)-weighted sequence, also fat suppressed. Both sequences were characterized with test objects (T1 ranging from 30 ms to 2,400 ms) and calibration curves were obtained to enable T1 calculation. The reproducibility and accuracy of the calibration curves were also investigated. Healthy volunteers and patients were scanned with Ethics Committee approval. The effect of B0 field inhomogeneity was assessed in test objects and healthy volunteers. The T1 of breast tumors was calculated at different time points (pre-, peak-, and post-contrast agent administration) for 20 patients, pre-treatment (10 lobular and 10 ductal carcinomas) and the two cancer types were compared (Wilcoxon rank-sum test).

RESULTS

The calibration curves proved to be highly reproducible (coefficient of variation under 10%). T1 measurements were affected by B0 field inhomogeneity, but frequency shifts below 50 Hz introduced only 3% change to fat-suppressed T1 measurements of breast parenchyma in volunteers. The values of T1 measured pre-, peak-, and post-contrast agent administration demonstrated that the dynamic range of the DCE sequence was correct, that is, image intensity is approximately directly proportional to 1/T1 for that range. Significant differences were identified in the width of the distributions of the post-contrast T1 values between lobular and ductal carcinomas (P < 0.05); lobular carcinomas demonstrated a wider range of post-contrast T1 values, potentially related to their infiltrative growth pattern.

CONCLUSIONS

This work has demonstrated the feasibility of fat-suppressed T1 measurements as a tool for clinical studies. The proposed quantitative approach is practical, enabled the detection of differences between lobular and invasive ductal carcinomas, and further enables the optimization of DCE protocols by tailoring the dynamic range of the sequence to the values of T1 measured.

Differentiation of ductal carcinoma in situ versus fibrocystic changes by magnetic resonance imaging: are there pathognomonic imaging features?

Background In breast magnetic resonance imaging (MRI), the diagnosis of ductal carcinoma in situ (DCIS) remains controversial; the most challenging cause of false-positive DCIS diagnosis is fibrocystic changes (FC). Purpose To search for typical and pathognomonic patterns of DCIS and FC using a standard clinical MRI protocol. Material and Methods Consecutive patients scheduled for breast MRI (standardized protocols @ 1.5T: dynamic-T1-GRE before/after Gd-DTPA [0.1 mmol/kg body weight (BW)]; T1-TSE), with subsequent pathological sampling, were investigated. Sixteen MRI descriptors were prospectively assessed by two experienced radiologists in consensus (blinded to pathology) and explored in patients with DCIS (n = 77) or FC (n = 219). Univariate and multivariate statistics were performed to identify the accuracy of descriptors (alone, combined). Furthermore, pathognomonic descriptor-combinations with an accuracy of 100% were explored (χ² statistics; decision trees). Results Six breast MRI descriptors significantly differentiated DCIS from FC ( P_corrected < 0.05; odds ratio < 7.9). Pathognomonic imaging features were present in 33.8% (n = 100) of all cases allowing the identification of 42.9% of FC (n = 94). Conclusion Pathognomonic patterns of DCIS and FC were frequently observed in a standard clinical MRI protocol. Such imaging patterns could decrease the false-positive rate of breast MRI and hence might help to decrease the number of unnecessary biopsies in this clinically challenging subgroup.

Voxelwise analysis of simultaneously acquired and spatially correlated 18 F-fluorodeoxyglucose (FDG)-PET and intravoxel incoherent motion metrics in breast cancer

PURPOSE

Diffusion-weighted imaging (DWI) and ¹⁸ F-fluorodeoxyglucose-positron emission tomography (¹⁸ F-FDG-PET) independently correlate with malignancy in breast cancer, but the relationship between their structural and metabolic metrics is not completely understood. This study spatially correlates diffusion, perfusion, and glucose avidity in breast cancer with simultaneous PET/MR imaging and compares correlations with clinical prognostics.

METHODS

In this Health Insurance Portability and Accountability Act-compliant prospective study, with written informed consent and approval of the institutional review board and using simultaneously acquired FDG-PET and DWI, tissue diffusion (D_t ), and perfusion fraction (f_p ) from intravoxel incoherent motion (IVIM) analysis were registered to FDG-PET within 14 locally advanced breast cancers. Lesions were analyzed using 2D histograms and correlation coefficients between D_t , f_p , and standardized uptake value (SUV). Correlations were compared with prognostics from biopsy, metastatic burden from whole-body PET, and treatment history.

RESULTS

SUV||D_t correlation coefficient significantly distinguished treated (0.11 ± 0.24) from nontreated (-0.33 ± 0.26) patients (P = 0.005). SUV||f_p correlations were on average negative for the whole cohort (-0.17 ± 0.13).

CONCLUSION

Simultaneously acquired and registered FDG-PET/DWI allowed quantifiable descriptions of breast cancer microenvironments that may provide a framework for monitoring and predicting response to treatment. Magn Reson Med 78:1147-1156, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Combined reading of Contrast Enhanced and Diffusion Weighted Magnetic Resonance Imaging by using a simple sum score

OBJECTIVE

To improve specificity of breast MRI by integrating Apparent Diffusion Coefficient (ADC) values with contrast enhanced MRI (CE-MRI) using a simple sum score.

METHODS

Retrospective analysis of a consecutive series of patients referred to breast MRI at 1.5 T for further workup of breast lesions. Reading results of CE-MRI were dichotomized into score 1 (suspicious) or 0 (benign). Lesion's ADC-values (in *10-3 mm2/s) were assigned two different scores: ADC2: likely malignant (score +1, ADC ≤ 1), indeterminate (score 0, ADC >1- ≤ 1.4) and likely benign (score -1, ADC > 1.4) and ADC1: indeterminate (score 0, ADC ≤ 1.4) and likely benign (score -1, ADC > 1.4). Final added CE-MRI and ADC scores >0 were considered suspicious. Reference standard was histology and imaging follow-up of >24 months. Diagnostic parameters were compared using McNemar tests.

RESULTS

A total of 150 lesions (73 malignant) were investigated. Reading of CE-MRI showed a sensitivity of 100 % (73/73) and a specificity of 81.8 % (63/77). Additional integration of ADC scores increased specificity (ADC2/ADC1, P = 0.008/0.001) without causing false negative results.

CONCLUSION

Using a simple sum score, ADC-values can be integrated with CE-MRI of the breast, improving specificity. The best approach is using one threshold to exclude cancer.

KEY POINTS

ADC is used to assign levels of suspicion to breast lesions. ADC values >1.4 *10 (-3)   mm (2) /s are likely benign and effectively rule out malignancy. ADC values below ≤1*10 (-3)   mm (2) /s) are likely malignant but may be false positive. CE-MRI (+1: suspicious, 0: benign) and ADC (0: indeterminate, -1: benign) scores are added. Sum scores >0 should be biopsied.

Intratumoral heterogeneity of the distribution of kinetic parameters in breast cancer: comparison based on the molecular subtypes of invasive breast cancer

PURPOSE

To evaluate the distribution pattern of kinetic parameters in breast cancers with various molecular subtypes.

MATERIALS AND METHODS

This study was approved by institutional review board and was compliant with HIPAA. We classified 192 invasive breast cancers of 186 patients into four molecular subtypes using hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) results and evaluated the distribution pattern of kinetic parameters (percent volume of kinetic types relative to the tumor volume) in the molecular subtypes.

RESULTS

In the delayed phase, all three types of kinetic parameter (persistent, plateau, and washout pattern) were observed in each molecular subtype without any dominant type of kinetic parameter. The percentages of washout pattern in the HR+ and HER2- type and triple negative (TN) cancers tended to be lower than those in the other molecular subtype cancers.

CONCLUSION

Each molecular subtype of invasive breast cancer showed a heterogeneous kinetic pattern in dynamic-contrast magnetic resonance imaging (MRI). The HR+/HER2- cancers and the TN cancers had relatively lower percentages of washout pattern. When a manual assessment of the kinetic parameters is performed, close attention should be paid in order to identify the malignant washout kinetic pattern, particularly in HR+/HER2- cancer and TN cancer.

A simple and robust classification tree for differentiation between benign and malignant lesions in MR-mammography

OBJECTIVES

In the face of multiple available diagnostic criteria in MR-mammography (MRM), a practical algorithm for lesion classification is needed. Such an algorithm should be as simple as possible and include only important independent lesion features to differentiate benign from malignant lesions. This investigation aimed to develop a simple classification tree for differential diagnosis in MRM.

METHODS

A total of 1,084 lesions in standardised MRM with subsequent histological verification (648 malignant, 436 benign) were investigated. Seventeen lesion criteria were assessed by 2 readers in consensus. Classification analysis was performed using the chi-squared automatic interaction detection (CHAID) method. Results include the probability for malignancy for every descriptor combination in the classification tree.

RESULTS

A classification tree incorporating 5 lesion descriptors with a depth of 3 ramifications (1, root sign; 2, delayed enhancement pattern; 3, border, internal enhancement and oedema) was calculated. Of all 1,084 lesions, 262 (40.4 %) and 106 (24.3 %) could be classified as malignant and benign with an accuracy above 95 %, respectively. Overall diagnostic accuracy was 88.4 %.

CONCLUSIONS

The classification algorithm reduced the number of categorical descriptors from 17 to 5 (29.4 %), resulting in a high classification accuracy. More than one third of all lesions could be classified with accuracy above 95 %.

KEY POINTS

• A practical algorithm has been developed to classify lesions found in MR-mammography. • A simple decision tree consisting of five criteria reaches high accuracy of 88.4 %. • Unique to this approach, each classification is associated with a diagnostic certainty. • Diagnostic certainty of greater than 95 % is achieved in 34 % of all cases.

Are the imaging features of the pleomorphic variant of invasive lobular carcinoma different from classic ILC of the breast?

The aim of this study was to evaluate whether pleomorphic invasive lobular carcinoma (PILC) is different from classic invasive lobular carcinoma (CILC) in terms of radiologic and clinicopathologic features. We compared the radiologic and clinicopathologic features of 22 surgically confirmed PILCs in 21 patients from 2004 to 2009 and 47 CILCs from 47 consecutive patients. For all cases, we reviewed the imaging findings, medical records and pathological results. PILC had a higher T stage, N stage, nuclear and histologic grade compared to CILC. PILC was more commonly negative for estrogen receptors and positive for HER2 than CILC (all p < 0.05). However, there were no significant differences in age, symptoms, tumor size, extensive intraductal component, lymphovascular invasion, triple negative profile, or multiplicity between the two groups. PILC was not detected on mammography in 1 (4.5%) of 22 cases, whereas CILC was not detected on mammography in 7 (14.9%) of 47 cases and on MRI in 2 (5.0%) of 40 (p = 0.42 and p = 1.000, respectively). MRI identified more frequent multiplicity than mammography for both PILC and CILC (p < 0.001), but was similar to US (p = 0.066). Most lesions showed a spiculated mass or architectural distortion with or without calcifications on mammography and ultrasound. No differences in mass and/or non-mass lesions or kinetics on MRI were observed between the two groups. PILC shows more pathologically aggressive features, but cannot be differentiated from CILC based on imaging findings.

Do patients with invasive lobular breast cancer benefit in terms of adequate change in surgical therapy from a supplementary preoperative breast MRI?

BACKGROUND

Breast magnetic resonance imaging (MRI) has been introduced in the preoperative management of invasive lobular breast cancer (ILC). We analysed if MRI leads to adequate changes in surgical management.

PATIENTS AND METHODS

We carried out a single-centre retrospective confirmatory analysis of 92 patients with ILC and a preoperative breast MRI. By applying a blinded tumour board method, we analysed if surgical procedures were altered due to breast MRI. In case of alteration, we analysed whether the change was adequate according to the postoperative pathology findings. We considered an adequate rate of change>5% to be a clinically relevant benefit.

RESULTS

A change in surgical therapy due to the MRI findings occurred in 23 of 92 patients (25%). According to the postoperative pathology findings, this change was adequate for 20 of these patients (22%; 95% confidence interval [CI] 14%-31%, P<0.0001). An overtreatment occurred for three patients (3%; 95% CI 0%-6%) who underwent a mastectomy following the results of breast MRI. Patients with larger tumours did likely benefit more from preoperative breast MRI.

CONCLUSIONS

Patients with ILC might benefit from a preoperative breast MRI. Possible harm from overtreatment should be minimised by diligent use of preoperative histological clarification.

Cyanine dyes as contrast agents for near-infrared imaging in vivo: acute tolerance, pharmacokinetics, and fluorescence imaging

We compare pharmacokinetic, tolerance, and imaging properties of two near-IR contrast agents, indocyanine green (ICG) and 1,1(')-bis-(4-sulfobutyl) indotricarbocyanine-5,5(')-dicarboxylic acid diglucamide monosodium salt (SIDAG). ICG is a clinically approved imaging agent, and its derivative SIDAG is a more hydrophilic counterpart that has recently shown promising imaging properties in preclinical studies. The rather lipophilic ICG has a very short plasma half-life, thus limiting the time available to image body regions during its vascular circulation (e.g., the breast in optical mammography where scanning over several minutes is required). In order to change the physicochemical properties of the indotricarbocyanine dye backbone, several derivatives were synthesized with increasing hydrophilicity. The most hydrophilic dye SIDAG is selected for further biological characterization. The acute tolerance of SIDAG in mice is increased up to 60-fold compared to ICG. Contrary to ICG, the pharmacokinetic properties of SIDAG are shifted toward renal elimination, caused by the high hydrophilicity of the molecule. N-Nitrosomethylurea (NMU)-induced rat breast carcinomas are clearly demarcated, both immediately and 24 h after intravenous administration of SIDAG, whereas ICG shows a weak tumor contrast under the same conditions. Our findings demonstrate that SIDAG is a high potential contrast agent for optical imaging, which could increase the sensitivity for detection of inflamed regions and tumors.

Assessing the degree of collinearity among the lesion features of the MRI BI-RADS lexicon

PURPOSE

To retrospectively assess collinearity among lesion feature of the MRI BI-RADS lexicon. Collinearity denotes a situation in which two or more (independent) variables are correlated to some degree, thus partly conveying the same information. Collinearity may cause problems in the interpretation of logistic regression models.

MATERIALS AND METHODS

We analysed the BI-RADS features of 351 lesions in 325 consecutive patients. Patients with biopsy proven breast disease or treated with chemotherapy were excluded. All lesion features were dichotomised into "present" or "not present". Correlation matrices were generated for mass and non-mass lesions separately, focus lesions were omitted. The phi coefficient was used as measure for correlation.

RESULTS

There were 253 mass (175 malignant, 78 benign), 66 non-mass (21 malignant, 45 benign) and 32 focus (5 malignant, 27 benign) lesions among the study population. The strongest inter-subgroup correlations among mass lesion features were: slow initial enhancement with persistent kinetics, phi=0.64 (0.56-0.71), rapid initial enhancement with washout kinetics, phi=0.52 (0.43-0.61) and rapid initial enhancement with persistent kinetics, phi=-0.43 (-0.53 to -0.32). The strongest inter-subgroup correlation among non-mass lesion features were: rapid initial enhancement with washout kinetics, phi=0.51 (0.30-0.67), slow initial enhancement with persistent kinetics, phi=0.43 (0.21-0.61) and rapid initial enhancement with persistent kinetics, phi=-0.41 (-0.18 to -0.60).

CONCLUSION

There is a noticeable overlap of information, especially between kinetic features and initial enhancement types for both, mass and non-mass lesions. This should be considered when generating logistic regression models with the MRI BI-RADS lesion features.