MRI of the breast: state of the art.

Contrast-enhanced MRI of the breast is probably the most sensitive method to detect breast pathology. It is best used to improve the sensitivity of mammography and sonography in selected patient groups with high breast cancer prevalence, where conventional methods are known to be less sensitive. Despite the high sensitivity of MRI, 5-12 % of invasive carcinomas are not recognized during MRI, because of lack of the typical criteria of carcinoma. MRI is probably inferior to mammography in detecting ductal in-situ carcinoma or very small carcinomas (< 3 mm), because the neo-angiogenesis induced by these small carcinomas is too faint to be detected by contrast-enhanced MRI. These tumours cannot be excluded by a normal MRI examination. MRI is non-specific as the distinction of benign and malignant breast lesions is unreliable. Only in selected cases (fat- or blood-containing lesions) may it improve the specificity of mammography and sonography. Mostly image-guided core biopsy is by far the most specific and least expensive method to establish a definitive diagnosis. For lesions exclusively detected by contrast-enhanced MRI, simple and reliable localisation devices are urgently needed. Presently accepted indications for MRI of the breast are: patients with silicone implants after mastectomy or augmentation mammoplasty (detection of recurrence/prosthesis rupture/silicon leakage); patients whose breasts are difficult to evaluate by combined mammography and sonography, who have had breast conservation therapy (local recurrence), or who have proven carcinoma in one breast (multifocality/-centricity or contralateral breast carcinoma) or proven axillary lymph node metastases from an unknown primary tumor, especially when these are hormone receptor positive; patients with extensive postoperative scarring. In the future, genetically defined high breast cancer risk may become an indication.