Pearls and pitfalls of MR lymphography in gynecologic malignancy

Dissemination of tumor to lymph nodes is one of the principal routes of metastatic disease. The presence or absence of nodal disease is an important prognostic factor in gynecologic malignancies; thus, nodal staging is an integral part of the pretreatment assessment. It is vital that pretreatment nodal staging be accurate and reliable. Current imaging techniques such as computed tomography and magnetic resonance (MR) imaging have limitations because they rely almost exclusively on size criteria. MR lymphography uses a lymph node-specific contrast agent (ferumoxtran-10) composed of ultrasmall superparamagnetic iron oxide particles. The contrast agent is taken up by macrophages within benign lymph nodes and allows differentiation from malignant nodes on the basis of alterations in signal intensity. This technique has been shown to increase the sensitivity and specificity of detection of lymph node metastases independent of nodal size. However, as with any technique, there are pitfalls that the radiologist must be aware of to avoid interpretative errors.