Enhancing nonmass lesions in the breast:: Evaluation with proton (1H) MR spectroscopy

Purpose: To prospectively evaluate the sensitivity and specificity of proton (hydrogen 1 [H-1]) magnetic resonance (MR) spectroscopy for diagnosing malignant enhancing nonmass lesions identified at breast MR imaging, with histologic examination as the reference standard. Materials and Methods: In this MPAA-compliant, institutional review board-approved study, in which all participants gave written informed consent, proton (H-1) MR spectroscopy of the breast was performed in suspicious or biopsy-proved malignant lesions that were 1 cm or larger at MR imaging. Single-voxel proton (H-1) MR spectroscopic data were collected. MR spectroscopic findings were defined as positive if the signal-to-noise ratio of the choline resonance peak was 2 or greater and as negative in all other cases. MR spectroscopic results were then compared with histologic findings, and statistical analysis was performed. Results: In 32 women (median age, 48.5 years [range, 20-63 years]) with enhancing nonmass lesions, the median lesion size at MR imaging was 2.8 cm (range, 1.2-9.0 cm). At histologic analysis, 12 (37%) of 32 lesions were malignant and 20 (63%) were benign. Positive choline findings were present in 15 of 32 lesions, including all 12 (100%) cancers and three (15%) of 20 benign lesions, giving proton (H-1) MR spectroscopy a sensitivity of 100% (95% confidence interval [CI]: 74%, 100%) and a specificity of 85% (95% CI: 62%, 97%) for detection of enhancing nonmass lesions. For 25 lesions with unknown histologic features, proton (H-1) MR spectroscopy would have significantly (P < .01) increased the positive predictive value of biopsy from 20% to 63%. If biopsy had been performed for only those lesions with positive choline findings at proton (H-1) MR spectroscopy, biopsy alight have been avoided for 17 (68%) of 25 lesions, and no cancers would have been missed. Conclusion: Proton (H-1) MR spectroscopy had 100% sensitivity and 85% specificity for the detection of malignancy in enhancing nonmass lesions.