Among MR imaging-detected breast lesions referred for biopsy, carcinoma was found in 25%, of which half were DCIS. Features with the highest PPV were spiculated margin, rim enhancement, and irregular shape for mass lesions and segmental or clumped linear and ductal enhancement for nonmass lesions. Final assessment categories were significant predictors of carcinoma.

In women with recently diagnosed breast cancer, MR imaging of the contralateral breast led to a biopsy recommendation in 32%. Cancer was found in 20% of women who underwent contralateral breast biopsy and in 5% of women who underwent contralateral breast MR imaging.

Purpose To study the differentiation of malignant breast lesions from benign lesions and fibroglandular tissue (FGT) using apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) parameters. Materials and Methods This retrospective study included 26 malignant and 14 benign breast lesions in 35 patients who underwent diffusion-weighted MRI at 3.0T and nine b-values (0–1000 s/mm2). ADC and IVIM parameters (perfusion fraction fp, pseudodiffusion coefficient Dp, and true diffusion coefficient Dd) were determined in lesions and FGT. For comparison, IVIM was also measured in 16 high-risk normal patients. A predictive model was constructed using linear discriminant analysis. Lesion discrimination based on ADC and IVIM parameters was assessed using receiver operating characteristic (ROC) and area under the ROC curve (AUC). Results In FGT of normal subjects, fp was 1.1 ± 1.1%. In malignant lesions, fp (6.4 ± 3.1%) was significantly higher than in benign lesions (3.1 ± 3.3%, P = 0.0025) or FGT (1.5 ± 1.2%, P < 0.001), and Dd ((1.29 ± 0.28) × 10−3 mm2/s) was lower than in benign lesions ((1.56 ± 0.28) × 10−3 mm2/s, P = 0.011) or FGT ((1.86 ± 0.34) × 10−3 mm2/s, P < 0.001). A combination of Dd and fp provided higher AUC for discrimination between malignant and benign lesions (0.84) or FGT (0.97) than ADC (0.72 and 0.86, respectively). Conclusion The IVIM parameters provide accurate identification of malignant lesions.

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On MRI, background parenchymal enhancement and fibroglandular tissue both decrease after menopause. The reduced postmenopausal enhancement is more marked in parenchyma than fibroglandular tissue. Background enhancement and fibroglandular tissue seen on MRI are under hormonal influence.

MR imaging-guided needle localization can be performed quickly and safely with commercially available equipment. The positive predictive value of MR imaging-guided needle localization (30.7%) was comparable to that reported for mammographically guided needle localization and was highest in women with synchronous breast cancer.

Complete excision rather than sampling of the mammographic target was associated with lower frequencies of discordance and ductal carcinoma in situ underestimation but had no other advantage or disadvantage. Among cancers in which the mammographic target was excised, surgery revealed residual cancer in almost 80%.

The objective of this study was to evaluate the impact of tamoxifen treatment on amount of fibroglandular tissue (FGT), background parenchymal enhancement (BPE), and cysts on breast MRI. Retrospective search identified 96 women with breast cancer who had a breast MRI both before and during adjuvant tamoxifen therapy between 2002 and 2008. After exclusion of all irradiated breasts, 88 women were eligible. Two readers blinded to tamoxifen treatment status independently rated level of BPE, amount of FGT, and cysts using a 4-point categorical scale: BPE--Minimal, Mild, Moderate, Marked; FGT--Fatty, Scattered, Heterogeneously Dense (HD), Dense; Cysts--Minimal, Mild, Moderate, Marked. A consensus interpretation was reached in cases of disagreement. During tamoxifen, there was a significant shift from higher to lower degree BPE, cysts, and FGT compared with before tamoxifen. BPE, cysts and FGT decreased in 68% (60/88), 38% (33/88), and 40% (35/88) of women during tamoxifen (p<0.001 for all measures). After the exclusion of all cases with minimal BPE, cysts, or FGT on the pre-tamoxifen MRI, the percentage of women demonstrating a decrease in these factors increased to 81% (60/74), 77% (33/43), and 41% (35/86), respectively. Exclusion of patients treated with chemotherapy did not substantially change these results. The percentage of women with decreases in FGT and cysts increased with greater duration on tamoxifen, whereas decreases in BPE were detected early in treatment (<90 days) and did not change substantially with longer duration on tamoxifen. A significant association exists between treatment with tamoxifen and decreases in BPE, cysts, and FGT on breast MRI.