Lymph nodes are part of the body immune system which are located throughout the body including head and neck, armpit, and groin.~Lymphadenopathy is defined as an abnormality in the size or character of lymph nodes caused by the invasion or propagation of either inflammatory or neoplastic cells into the nodes.~The differentiation of malignant from benign lymph nodes is essential because it predicts the patient prognosis and help in the decision making regarding the management plan.~On ultrasound, gray scale sonography helps to evaluate nodal morphology, whilst color doppler is used to assess vascular pattern. The qualitative criteria for malignancy were heterogenous hypoechoic cortex, irregular margins, lack of hyperechoic fatty hilum and abnormal blood vessels penetrating the lymph nodes capsule.The avascular or hilar patterns were defined as LNs with normal vascularity pattern, and the peripheral or mixed (peripheral and hilar) pattern as LNs with abnormal vascularity pattern. On B-mode and color doppler ultrasound, there is no specific criteria for differentiating metastatic lymph nodes from reactive lymph nodes with 100% accuracy.~Fine-needle aspiration biopsy is the reference standard for differentiating metastatic lymph nodes from reactive lymph nodes. However, restrictions of fine-needle aspiration biopsy are that it is an invasive procedure, and it is not possible to perform for lymph nodes smaller than 5 mm.Therefore, a simple, reliable, and non-invasive imaging modality for differentiating malignant lymph nodes is required.~Ultrasound elastography (UE) is a rather new, non-invasive imaging technique that can be used to depict tissue stiffness and elastic properties. Ultrasound elastography (UE) can be divided broadly into 2 groups depending on the type of tissue displacement:~Strain elastography (SE): measures tissue displacements along the axis of an applied force.Strain elastography provides semi - quantitative scores based on elastographic pattern (scores based on percentage of stiff area within the lesion) and strain ratio (ratio between the lesion and the background tissue).~Shear wave elastography (SWE): measures a different type of waves that is also produced when tissues are mechanically stimulated. Shear wave elastography is also a quantitative method of analysis for elasticity images using shear wave speed (m/s) or elastic modulus (kPa).~Ultrasound elastography (UE) is easy, rather cheap, non-invasive, and quick to perform, well tolerated by patients, and offers a strong diagnostic power.
Evaluation of the role of Ultrasound Elastography in differentiation between benign and malignant lymph nodes and its additional information over the classic gray scale and color Doppler ultrasound.