High-resolution lymphoscintigraphy is essential for recognition of the significance of internal mammary nodes in breast cancer

Background: Sentinel node biopsy (SNB) of internal mammary nodes (IMNs) in breast cancer is controversial. Most centers rarely identify IMN on lymphoscintigraphy but others report up to 45% of cases. Controversy relates to the technique of lymphatic mapping, safety of IMN SNB, the significance of positive IMN, and potential to impact survival. Methods: Assessment of drainage rates from two unrelated nuclear medicine departments' databases. Review of related literature. Results: High-resolution lymphoscintigraphy results in IMN drainage in one-third of breast cancers. There is a learning curve for the technique. In 1754 consecutive cases, internal mammary drainage occurred in 53% of medial tumors, 37% midline tumors and 24% of lateral tumors (overall 34%). Extended radical mastectomy series also demonstrate the (approximately) 1/3 ratio when comparing IMN positivity rates to axillary node positivity rates (18.8% : 48.3%) and in node-positive patients (31% : 100%). The management altering potential of IMN assessment and potential survival impact are discussed. Conclusions: IMN mapping gives information that alters management in up to one-third of cases. These rates of IMN drainage are reproducible and reflect lymphatic density and anatomy of the breast. A priority need exists to establish a collaborative clinical trial to clarify the value of IMN assessment.