“What Should We Know About Lymph Nodes”

Abstract

Lymph nodes are involved in a wide variety of diseases, particularly in cancer. In the latter, precise nodal staging is essential to guide therapeutic options and to determine prognosis. In patients with cancer, the demonstration or exclusion of lymph node metastases is an important component of tumor staging besides evaluation of local tumor extent and has crucial implications for the patient's prognosis and therapeutic strategy, especially when deciding on curative versus palliative treatment. The lymphatic drainage of the breast is of great importance in the spread of carcinoma and about three quarters of it is to the axillary nodes. There are three surgical levels of axillary lymph nodes:

level I: below the lower edge of the pectoralis minor muscle. level II: underneath/posterior the pectoralis minor muscle. level III: above/medial the pectoralis minor muscle.

In many settings, the ability to detect axillary lymph nodes containing metastases with imaging and image-guided biopsy can allow surgeons to bypass sentinel lymph node dissection and proceed with full axillary lymph node dissection. However, no imaging modality currently has sufficient negative-predictive value to obviate surgical staging of the axilla if no abnormal lymph nodes are detected. In many settings, the ability to detect axillary lymph nodes containing metastases with imaging and image-guided biopsy can allow surgeons to bypass sentinel lymph node dissection and proceed with full axillary lymph node dissection. However, no imaging modality currently has sufficient negative-predictive value to obviate surgical staging of the axilla if no abnormal lymph nodes are detected. Currently, the most accepted and useful modality for imaging axillary lymph nodes is ultrasonography. Advantages of MRI over sonographic evaluation of the axilla include the ability to compare directly axillary lymph nodes in question with the contralateral axilla and decreased dependence on operator experience. Finally, the increased availability of functional imaging, especially through the use of FDG-PET, has greatly contributed to the accuracy improvement of nodal metastases identification. The aim of this review will thus be to briefly review the anatomy and physiology of the lymphatic systems and to overview the basic principles of up-to-date lymph node imaging.