Intramammary lymph nodes and breast cancer: a marker for disease severity, or just another lymph node?

Background Axillary lymph node status is still considered the most significant prognostic factor for breast cancer outcome, and treatment decisions are based on the presence or absence of nodal disease. Intramammary lymph nodes (IMLNs) can be a site of regional spread. Is this a marker for more aggressive disease? Methods We reviewed the cancer center pathology database from 1991 to 2005 for all cases of breast cancer with IMLNs. Results IMLNs were identified in 64 breast cancer patients, with metastatic spread in 20 patients, and benign IMLNs described in 44 patients. Positive IMLNs were associated with more aggressive disease, including higher rates of invasive versus noninvasive cancers (5% ductal carcinoma-in-situ [DCIS] with positive IMLNs vs. 23% with negative IMLNs), lymphovascular invasion (55% vs. 11%), and a higher rate of axillary lymph node involvement (72% vs. 18%). Patients with positive IMLNs were also more likely to undergo mastectomy (75% vs. 54%). Conclusions IMLN metastases are a marker for disease severity; recognition of this may influence choice of adjuvant therapy. The presence of metastatic disease in an IMLN is associated with a high rate of axillary nodal involvement, and should mandate axillary dissection. Preoperative lymphoscintigraphy may help identify these extra-axillary metastases.