The radiologist also needs information on the patient’s current therapy and previous treatment, as such knowledge may influence interpretation. In order to provide the best possible assessment of nodal status with CT and MR, the radiologist requires detailed knowledge of: (1) the primary tumour in terms of the patterns of spread and the incidence of nodal metastases at different stages of disease (2) the characteristic CT/MR features of nodal involvement (3) the pitfalls in diagnosis of nodal disease (4) the accuracy of imaging and the impact of positive and negative results on patient management. This frequently requires discussion with clinicians or review of the patient’s case notes. In order to give appropriate consideration to the likelihood of a prominent or enlarged lymph node harbouring a metastasis, it is incumbent on the radiologist to use all the relevant information available. It is therefore likely to be used, at least for the foreseeable future, in highly selected patient groups. MR lymphography can demonstrate small nodal deposits, but the technique remains in the research arena, requires high-resolution thin sections to produce good image quality and is expensive.

However, the results of CT and MR imaging have been disappointing with poor sensitivities and specificities, low sensitivities being due to the inability to identify metastases in normal-sized nodes or those that are only minimally enlarged, and poor specificities resulting from nodal enlargement due to benign pathology. Pre-treatment detection of malignant nodes determines patient management, frequently distinguishing surgical candidates from those best suited to non-surgical therapy. The accurate detection of lymph node metastases is one of the most important challenges in cancer imaging today, for the presence of nodal disease is a powerful adverse prognostic indicator.

Shotty right inguinal lymph nodes