This study was a retrospective analysis, approved by the ethics committee during the period from October 2014 to March 2015, in which we analyzed the contrast-enhanced MRI morphology descriptors and kinematic curve in 100 patients with triple-negative breast cancer as compared to another 100 patients (control group) of the same age group with different molecular subtypes.
Patients
It included 200 patients who were subjected to MRI scanning including pre-contrast and dynamic post-contrast sequences.
Inclusion criteria
Patients proved to have breast carcinoma of different molecular subtypes.
Exclusion criteria
- Cases that lacked pathological confirmation
- Cases proved to be benign
Methods
MR imaging
MRI was performed for the breasts using 1.5-T magnet scanners by two devices (Intera and Achieva, Philips medical system). All patients were examined in the prone position using a dedicated phased array breast coil with eight channels. Total study time ranged from 30 to 45 min. No sedation was used.
MRI imaging protocol
-
A.
Cases were examined first by pre-contrast sequences
Axial T1-weighted images, sagittal and axial T2-weighted images, axial short time inversion recovery (STIR), and a pre-contrast fat-saturated T2-weighted pulse sequence. Pre-contrast images are obtained over a 512 × 192 matrix in the axial plane with a slice thickness of 4 mm without gap, flip angle = 90° and FOV = 34–37 cm.
- B.
Dynamic contrast-enhanced series
A bolus of contrast (Magnevist (gadopentetatedimeglumine) 0.1 mmol/kg) was injected manually intravenous.
Post-processing and image analysis
Post-processing image subtraction was obtained using the software subtraction function available on the work station to highlight the enhancing features in the image.
- 1.
Quantitative analysis was done by using time/signal intensity curve.
A color overlay map was displayed, indicating regions of threshold enhancement.
- 2.
The maximum intensity projection (MIP) (Fig.1a) was performed to demonstrate the distribution of disease in the breast in relation to the skin, nipple, chest wall, and large vessels.
Image analysis
Magnetic resonance images were reviewed by two radiologists in the same setting, and the final diagnosis was reached by their agreement (in consensus). The findings of dynamic contrast-enhanced MRI study were evaluated in accordance with the ACR BI-RADS MRI Lexicon, 2013, that includes two major categories of descriptors: morphology and enhancement kinetics.
- A.
Morphology descriptors
Enhancing lesions were categorized as focus, mass, and non-mass enhancement.
- 1.
Focus/foci: A focus is a breast lesion smaller than 5 mm (Fig. 2d).
- 2.
Mass: A mass is a three-dimensional space-occupying lesion (Fig. 1).
- (a)
Multiplicity of masses
- (b)
Mass was characterized by the following:
Shape (oval, round, irregular), margin (circumscribed, not circumscribed) (Fig. 2), and internal enhancement characteristics (homogenous, heterogenous, rim enhancement (Fig. 3), dark internal septations).
- 3.
Non-mass enhancement
- (a)
Distribution pattern
- (b)
Internal enhancement characteristics
Homogenous
Heterogeneous
Clumped
Clustered ring
- B.
Associated features
Associated findings with or without enhancement which include nipple retraction or inversion, skin retraction, thickening or invasion, lymphadenopathy, pectoral muscle invasion and chest wall invasion, architectural distortion, high signal intensity in ducts on unenhanced images, abnormal signal void, hematoma, edema, and cysts were reported.
Signs of spread of malignancy: On the MR images of the breast, spread to the axillary region, other lymph nodes, the chest wall muscles, the ribs, the adjacent pleura and lung, or the overlying skin was reported.
- C.
Kinetic enhancement curve assessment
Three enhancement patterns were identified on the basis of the time/signal intensity curve: types I, II, and III (Fig. 3g).
All patients were assigned a BI-RADS category [6] according to the ACR MRI BI-RADS lexicon.
Statistical analysis
The data was summarized using number and percentage for qualitative variables and mean and SD for normally distributed quantitative variables. Comparison between groups was done using the chi-square test for qualitative variables and the independent T test for quantitative variables. P value less than or equal to 0.05 was considered statistically significant, and 0.01 or less considered highly significant.