Chest ImagingSterilized lymphoma
residual
mediastinal masses following treatment of lymphomas. These masses reflect often residual fibrous tissue components of the
tumour itself, or post-treatment
fibrosis. Pathologically, residual masses in patients with treated
Hodgkins disease (
HD) consist of almost acellular, hyalinized fibrous tissue. Such residual masses can be seen in as many as 80% of patients with
HD and 40% of patients with
non Hodgkins lymphoma.
Calcification may occur in
mediastinal lymph node sites following treatment with radiation or chemotherapy. Typically these calcifications exhibit an eggshell distribution (
Fig.1) (see
calcification mediastinal lymph node).
Patients showing complete resolution of the lymphoma on CT scan are generally considered to have had a satisfactory response. However, monitoring the disease in terms of tumour size is not always an accurate measure of treatment success. It is difficult using CT alone to differentiate residual masses due to fibrosis from active or recurrent disease. CT attenuation is identical for both active and inactive residual masses in patients treated for lymphoma. MRI may make the differentiation more accurately. On T2-weighted images, a node replaced by fibrosis will have a low signal intensity in contrast to a node that contains active tumour; the tumoural node will exhibit a homogeneous or heterogeneous hyperintense pattern. Inflammation and necrosis may, however, be present in the early post-therapy phase, and as a result, a hyperintense pattern depicted in the lesions may simulate active tumour. Only active pattern observed beyond 46 months after therapy may lead to a suggested diagnosis of residual tumour. Reappearance of foci of high signal intensity in residual masses is a strong indicator of early recurrence and is usually noted before the occurrence of clinical symptoms (see lymphoma recurrence thoracic). Gallium-67 scanning tumour cell viability may also be used in distinguishing active tumour from residual masses. In addition, the use of FDG positron emission tomography to assess tumour metabolic activity may be helpful.
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Contrast-enhanced CT scan in a patient previously treated by mantle radiation therapy for Hodgkin's disease (HD), showing eggshell calcifications in anterior mediastinal and right hilar lymph nodes. A residual mass of post-treatment fibrosis is also present in the prevascular mediastinal space.
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Sterilized lymphoma, Fig.1 | |