Introduction 1 5 3 1 5 6 1 5 7 8 8 9 1 7 5 5 10 5 11 2 11 12 13 The morphologic aspects of ILC are not yet well defined, nor is the dynamic behavior of contrast agents in these tumors clearly documented. Moreover, whether the MRI findings are similar to pathologic findings and can thus be used for accurate staging still needs to be established. Finally, the impact of MRI on surgical treatment of ILC should be evaluated. Materials and methods Search strategy We performed a literature search for articles that specifically dealt with the use of MRI in patients with histologic proof of ILC published before 1 April 2006. The Cochrane Library, MEDLINE and the in-progress citations as provided by PubMed were searched using the query: “lobular AND (MR OR MRI OR MRT OR magnetic).” These databases were further searched using the “Related Articles” function in PubMed. The same query was used to browse the web using scholar.google.com. Furthermore, the references of all retrieved articles were manually searched for relevant cross-references. Articles in all languages were accepted. All retrieved articles were then compared and from overlapping series of patients only the most recent publication was accepted. Many different search terms were used for literature review of other imaging modalities. However, only PubMed was used as search engine. Endpoints What is the sensitivity of MRI for ILC? What are the visual characteristics of ILC on MRI? Are the findings on MRI equal to the findings at pathology? What is the impact of MRI on surgical management of ILC? 14 Eligibility criteria Detection Morphology Dynamic curve analysis of contrast behavior Quantitative analysis of contrast behavior Relative correlation with pathology Absolute correlation with pathology Detection of additional lesions Impact on surgical treatment Statistics 15 Z 16 Q I 2 Q χ 2 I 2 I 2 17 Q p In cases where meta-analysis was feasible, the estimate and the 95% CL are expressed. When meta-analysis was not feasible due to severe heterogeneity, only the range of values found in the different studies is mentioned. All calculations were performed using R version 2.3.1 (The R Project for Statistical Computing, www.r-project.org) and the meta package (G. Schwarzer, cran.r-project.org). Results Studies 18 38 39 42 20 21 29 37 18 27 42 1 Table 1 Characteristics of the included studies Authors a b c d e f g h i j k l 32 1996 1 20 60 38 84 2 1 1 0 X 11 34 1998 1 23 X X X 1 2 2 0 X 11 36 2001 1 17 53 32 69 2 2 1 1 1,7 12 41 2001 1 12 m m m 2 2 1 0 m 12 35 2001 1 28 X 32 81 2 2 2 0 X 9 24 2001 2 22 X X X 2 2 2 0 3,7 12 30 2002 1 13 55 46 84 2 1 1 0 X 11 28 2002 1 20 61 39 78 2 3 2 0 X 11 38 2003 1 19 59 42 79 2 2 2 0 4,1 11 26 2003 1 21 57 43 72 2 2 1 0 X 11 31 2003 1 62 53 X X 2 2 3 1 X 10 39 2003 1 24 m X X 2 0 0 1 X 10 33 2004 1 26 57 41 74 3 2 2 0 X 11 22 2004 1 17 X X X 0 0 0 0 X 10 19 2004 1 34 55 35 78 2 2 2 0 4,9 10 40 2004 2 29 X X X 3 2 2 0 X 13 25 2005 1 29 62 51 67 2 1 3 0 X 9 23 2005 1 34 X X X 2 2 2 0 X 11 a b c d e f g h i j k l m 33 34 40 19 20 23 24 26 31 33 36 38 40 41 25 30 32 22 23 31 38 40 41 32 39 26 30 38 26 30 32 36 41 43 31 36 39 Lesion detection 19 23 24 26 28 33 34 40 Q p I 2 24 40 T p Q p I 2 Q p I 2 Q p I 2 1 Fig. 1 ILC MMG US CE horizontal lines right diamonds bottom MRI US  Morphology 23 30 32 33 36 38 41 41 38 14 Q p I 2 2 Table 2 Morphologic appearance of ILC on MRI Authors Number of tumors Non-mass-like Mass-like 32 20 1 (5) 19 (95) 36 18 8 (44) 10 (56) 30 13 9 (69) 4 (31) 38 20 11 (55) 9 (45) 33 27 6 (22) 21 (78) 23 35 11 (31) 24 (69) Numbers between parenthesis represent percentages 23 32 33 38 41 Kinetics 34 35 34 35 30 38 30 K trans 44 38 Correlation 19 24 26 28 32 33 40 26 32 33 3 Table 3 Relative correlation of unifocality versus multifocality for MRI versus pathology Authors Number of patients UF MRI UF PATH MF MRI MF PATH a b 32 20 9 11 11 9 2 1 26 21 9 10 12 11 1 0 33 26 14 17 12 10 2 1 Total 67     5 2 UF MF PATH a b Overestimation of multifocality based on mammography in 63 patients from these studies occurred in 2 patients (3%), whereas underestimation occurred 25 times (40%) and the lesion was not visible on mammography in another 4 patients (6%). 32 33 4 32 Table 4 Relative correlation of single quadrant versus multicentric involvement for MRI versus pathology Authors Number of patients SQ MRI SQ PATH MC MRI MC PATH a b 32 20 9 11 11 9 2 0 33 26 21 21 5 5 0 0 Total 46     2 0 SQ MC PATH a b Mammography in 42 of these patients resulted in overestimation of disease extent in 1 patient and underestimation in 15. Again, no lesion was visible in four patients. 40 19 24 26 28 32 32 Q p I 2 5 Table 5 Correlation of tumor size measured by various modalities compared to pathology Authors MRI MMG US CE N PCC Κ N PCC K N PCC K N PCC K 32 20  0.773 15  −0.081       28 20 0.97  10 0.66  14 0.67     26 21 0.86  21 a  21 a  21 0.47  24 22 0.87  16 0.79  20 0.56  19 0.89  19 36 0.81  36 0.34  36 0.24     25 33 0.88     9 0.71     MMG US CE N PCC K a 19 24 Additional lesions 22 23 31 33 36 Q p I 2 6 Table 6 Additional malignant findings in the ipsilateral breast by MRI Authors Number of patients Number of additional findings 36 18 7 31 51 11 33 26 9 22 17 9 23 34 8 Total 146 44 Meta-analysis (%) 100 32 7 19 22 25 28 31 40 Q p I 2 Table 7 Additional findings in the contralateral breast by MRI Authors Number of patients Number of contralateral findings 24 22 0 28 20 2 31 53 5 22 17 1 19 34 2 40 15 0 25 14 0 23 34 2 Total 206 12 Meta-analysis (%) 100 7 Effect on surgical treatment 23 26 28 31 32 39 Q p I 2 Q p I 2 8 Table 8 Changes in surgical management based solely on MRI findings Authors Number of patients Number of changes Correct changes Incorrect changes Correct wider excision Incorrect wider excision Correct mastectomy Incorrect mastectomy 32 20 8 7 1   7 1 28 20 3 3    3  26 21 5 5  1  4  31 51 11 11  5  6  39 24 11 9 2 NA NA NA NA 23 24 6 6  3  3  Total 160 44 41 3 9  23 1 Number of changes (%) 100 28.3       Correct changes (%)  100 88      Number of changes and correct changes show the result of meta-analyses NA 32 26 40 Discussion Studies and quality analysis 23 30 32 33 36 38 41 1 Sensitivity 10 45 47 10 45 51 52 51 40 28 28 40 40 47 53 58 47 56 57 59 13 60 63 34 64 57 Morphology 14 65 10 45 46 48 50 51 55 33 8 38 10 33 45 51 55 30 33 Kinetics 30 38 26 35 66 1 67 68 69 Correlation 5 51 52 70 71 70 1 5 67 72 19 32 Additional lesions and effect on surgical treatment Especially important in this analysis is the detection of additional lesions apart from the index lesion in patients with ILC. The co-existence of other invasive malignant lesions apart from the index lesion in the ipsilateral breast in 32% of patients only visualized by MRI is high. Moreover, the detection of contralateral cancer in another 7% of patients by MRI only, seems to make MRI indispensable. These findings are confirmed by the rate of change in treatment of the ipsilateral breast based on MRI. The fact that change in treatment was considered correct, as verified by pathologic findings in the specimen, in 88% of cases shows that ILC is often more extensive than appreciated on conventional imaging. 2 73 74 75 5 68 2 76 p 77 78 Conclusion Magnetic resonance imaging has a high sensitivity for ILC, not achieved by other imaging modalities. Therefore MRI is helpful in cases where conventional imaging is inconclusive. Morphology is often mass-like and a typical ILC presents as an irregular or spiculated mass. However, asymmetric enhancement that can be ductal, segmental, regional, or diffuse in nature may be the only sign of tumor. MRI measures disease extent with a high reliability. Although underestimation and overestimation of lesion size by MRI still occurs, it is more accurate than size determination by other modalities, indicating often more extensive tumor burden than expected. The underestimation by other imaging modalities results in more failure of BCT, more re-excisions and more conversion to mastectomy in series where MRI is not used. MRI has an effect on surgical management in that when used to assess disease extent, surgical management was changed in 28.3% of which 88% were judged necessary based on pathology. Larger series of patients are required to confirm the findings of this review; especially evaluation of tumor morphology and dynamic profile seems feasible.