Internal mammary lymph nodes as incidental findings at screening breast MRI.

OBJECTIVE: To evaluate the prevalence of internal mammary lymph nodes (IMLNs) on breast magnetic resonance imaging (MRI) in a screening population. MATERIALS AND METHODS: We retrospectively reviewed 92 consecutive screening breast MRI exams. Logistic regression was performed to ascertain the risk of IMLNs in cancer-free subjects and to determine whether the risk varies with age. RESULTS: IMLNs were present in 48.9% of patients. Mean node size was 4 mm (range, 3-10 mm). The prevalence of IMLNs was not related to age. No patients developed breast cancer after a mean follow-up of 3 years. CONCLUSION: Subcentimeter IMLNs are common incidental findings at screening breast MRI.