The Role of Magnetic Resonance Imaging in Assessment of Axillary Lymph Nodes Metastasis in Breast Cancer Patients.

The presence of axillary metastasis is important for prognosis and determining of treatment plan, so identification of axillary metastasis in early stage newly diagnosed breast cancer is important for staging of disease and treatment. However, approximately 40% of women who presents with early stage breast cancer also have axillary metastasis. The status of lymph nodes in patients with breast cancer used to be evaluated with axillary lymph node dissection. During the last 15 years, sentinel lymph node biopsy has replaced for grading of patients with clinically lymph node negative breast cancer. Despite being a less invasive method when compared to axillary lymph node dissection, sentinel lymph node biopsy also leads to complications such as lymphedema, seroma, localized swelling, pain, paresthesia, decrease in arm strength, infectious neuropathy and shoulder stiffness in 20% of patients. The imaging modalities for assessing the axillary lymph nodes are rapidly evolving. Ultrasound is applied widely for its convincing and dynamic observation. However, the sensitivity and specificity of ultrasound for lymph node metastasis were unreliable and controversial. Owing to radiation and relative lower diagnostic accuracy, computed tomography is limited in clinic. Positron emission tomography and positron emission tomography/computed tomography can reflect metabolism of glycolytic activity. Undoubtedly, they have shown the higher diagnostic significance in assessing distant metastasis and regional metastatic axillary lymph nodes, but their high radiation and expensive fee keep the common people away. Ultrasmall super paramagnetic iron oxide is the same. Magnetic resonance imaging is developing with an unimaginable speed. Over the past years, it has been used to evaluate axillary lymph nodes. Its sensitivity and specificity for metastatic axillary lymph nodes were higher than ultrasound and computed tomography. Diffusion weighted imaging is an advanced magnetic resonance imaging application which derives its image contrast from the differences in water mobility in the extracellular spaces, reflecting cellular density, organization, microstructure and microcirculation. Several studies have shown that diffusion weighted imaging can serve as a powerful tool for differentiating benign from malignant breast lesions. In addition to this use, diffusion weighted imaging may also be used in the assessment of axillary lymph nodes, since they show similar tissue characteristics to the primary tumor. Evaluation of lymph nodes is a promising novel application of diffusion weighted imaging , which can easily be applied as an adjunct to conventional breast magnetic resonance imaging . There are a few preliminary studies that have shown that diffusion weighted imaging can be used to detect lymph nodes affected by malignant cells. Koh reported that after the involvement of nodes with malignancy, they undergo changes and the increase in cellularity leads to diffusion restriction and low apparent diffusion coefficient values.