The radiological imaging of lymphoma has evolved with the development of computed tomography (CT) and, to a lesser extent, magnetic resonance imaging (MRI). These techniques have rendered obsolete staging laparotomies and lymphangiography.

CT
CT is the primary staging modality and it also serves as the main tool for monitoring disease response (Figs 1a & b) and relapse. In addition, it may aid percutaneous lymph- node biopsies.

Lymphoma can occur anywhere in the body, whether in the nodes or in extranodal locations. Initial staging work-up often includes imaging of the neck, thorax, abdomen, and pelvis. The imaging appearance can be quite variable depending on the site of involvement. Nonetheless, in typical cases the diagnosis can often be suspected from imaging findings although tissue diagnosis is required in all cases.

In nodal involvement, the principal imaging feature is that of lymphadenopathy. CT uses nodal size as the main but imperfect criterion for determining pathological involvement. In general, nodes greater than 1 cm in short-axis dimension are considered abnormal although this cut-off may vary depending on the location---i.e. the jugulodigastric node is considered abnormal only if greater than 1.5 cm. Splenomegaly is another common feature of lymphoma, with splenic infarcts seen as an occasional complication.

In extranodal disease, radiological diagnosis is challenging, especially in the absence of associated lymphadenopathy because the radiological appearance is often non-specific. Pulmonary parenchymal involvement, for instance, may present as single or multiple masses, and confluent airspace disease may mimic pneumonia or a reticular/reticulonodular interstitial pattern. Likewise, hepatic involvement may vary from a solitary mass to multifocal masses to diffuse infiltration and simulate hepatocellular carcinoma or metastases.

In the gastrointestinal tract, the imaging findings may range from circumferential wall thickening to a focal mural mass or polypoid mucosal lesions, all of which are non-specific.

Other imaging modalities

MRI is not routinely used in the assessment of lymphoma because it does not confer any significant advantage in most cases. It is, however, superior to CT in disease evaluation in some sites, such as the central nervous system and spine (Figs 2a,b & c) and orbits and may be preferred in these locations.

Plain radiographs are inadequate for staging purposes but may occasionally be used to monitor disease response in certain sites, mainly the mediastinum if there is bulky disease. However, complete response in such cases should always be confirmed with CT.

Finally, nuclear medicine studies such as gallium-67 scans and positron emission tomography (PET) may also be useful in evaluating the nature of residual masses after treatment to differentiate residual tumour from fibrous tissue.

Figure 1: CT scan in NHL

1a


1b


Patient with follicular lymphoma presenting with marked retroperitoneal adenopathy and splenomegaly (a). There is good response with decreased size of lymph nodes and resolution of splenomegaly (b) after two cycles of combination chemotherapy


Fig 2: MRI in NHL

2a


2b

2c

2 a, b & c

Post-contrast T1W MR image demonstrating central nervous system lymphoma affecting the splenium of the corpus callosum as well as leptomeninges on the left (a). These were not as well appreciated on the contrast CT (b). There is good resolution after treatment (c).

 

Dr Quek Swee Tian
Senior Consultant
Oncologic Imaging