• Lymphatic drainage of breast to which breast cancer can metastasize includes the axillary (ALN), internal mammary (IMLN), infraclavicular, or supraclavicular nodes. 3-12% of breast lymphatics drain to IM chain.
• Evaluation of regional lymph node status (N) is crucial for breast cancer disease staging, treatment planning, and prognosis. It is crucial to identify IMLN metastases; as if present it not only changes the nodal stage (it upstages the patient to clinical stage III disease at minimum) and prognosis of the patient but also affects the planning of radiation therapy.
• The independent risk factors that increase likelihood of IMLN metastasis include medial tumor location, large tumor size, more involved ALNs, age < 35 years, higher tumor grade, tumor with calcification, nipple inversion, triple-negative hormone receptor status, lymphovascular invasion and negative HER2 status.
Evaluation of the internal mammary nodes with parasternal real-time handheld US is a cost effective and convenient way to detect and upstage nodal metastases.