Multiple synchronous (multifocal and multicentric) breast cancer: clinical implications.

Multifocality in breast cancer is a frequent phenomenon, whose prevalence may vary between 13 and 75%. The differences in estimation of the prevalence of multifocality across studies may be explained by the differing definitions used for multifocality and multicentricity; this inconsistency makes it difficult to analyze the literature on the subject. The incidence of multifocality is probably often underestimated. Currently, the diagnosis relies on imaging. The performance of mammography is relatively low, but the addition of breast ultrasonography can improve diagnostic sensitivity. Recently, breast magnetic resonance imaging (MRI) has been shown to be more accurate for detecting multifocality compared to conventional imaging. However, this modality is associated with high rates of false-positives that could result in inappropriate disease management. Thus, the use of MRI is not recommended as a first-line technique for diagnosing multifocality. The diagnosis of multifocality is important for breast cancer management, particularly with regards to the choice of surgery. A finding of multifocality may spur a decision to perform a wider excision that will avoid positive margins. Regarding the results of conservative surgery in the presence of multifocality, studies are contradictory, and no international consensus exists. Multifocality may also modify the management of the axillary basin; studies have shown that multifocality is associated to an over-risk of 20% of lymph node invasion. The sentinel node biopsy has been considered as an alternative to complete axillary lymph node dissection by the American Society of Clinical Oncology. The prognostic value of multifocality is still not well known, although some studies have suggested that it is associated with a worst prognosis. Further studies are needed to better assess the impact of multifocality on breast cancer prognosis.