Invasive lobular carcinoma of the breast: spectrum of mammographic, US, and MR imaging findings.

The reported prevalence of invasive lobular carcinoma (ILC) is variable, with more recent studies indicating that ILC accounts for 10%-15% of all invasive breast carcinomas. However, the radiologic diagnosis and management of ILC can be uniquely challenging. Current imaging modalities are not very specific for differentiating ILC from other invasive breast cancers, and ILC has a tendency to have appearances at mammography that are atypical for invasive ductal carcinomas, resulting in higher false-negative rates. The clinical detection of ILC can also be difficult, since ILC frequently fails to form a palpable lesion. This tendency of ILC to have atypical imaging and clinical appearances is related to its histopathologic features and its failure to elicit a desmoplastic response. Despite these diagnostic challenges, however, imaging remains crucial in the detection and management of ILC. Mammography, ultrasonography (US), and magnetic resonance (MR) imaging all play important roles, with each modality having its own advantages and limitations. The use of US and MR imaging as adjuncts to mammography increases sensitivity in the detection of ILC and provides useful information for further management and presurgical planning. Familiarity with the spectrum of imaging appearances of ILC is essential. (c) RSNA, 2009.