Malignant lymphoma can present as a mass in anterior, superior, or middle mediastinum. It may appear in this area as
part of the manifestations of the disseminated process or as a primary mediastinal disease. The majority of malignant
lymphoma presenting as primary mediastinal neoplasm falls into the following three categories: Hodgkin's lymphoma,
lymphoblastic lymphoma, and large cell lymphoma, in order of frequency.
Intrathoracic disease is more common in Hodgkin's disease (HD) than non-Hodgkin's lymphoma (NHL). All of the
mediastinal nodal groups except the anterior diaphragmatic (paracardiac) and posterior mediastinal nodes are more
frequently involved with HD than NHL. Intrathoracic disease of NHL may follow the patterns described for HD. However,
the contiguity of nodal disease typical for HD is frequently absent in NHL. Involvement of the paratracheal and/or
prevascular nodal groups is the most common. These are followed by subcarinal nodes, cardiophrenic angle nodes,
internal mammary nodes, and posterior mediastinal nodes. In NHL, pulmonary or pleural lesions may be seen without
mediastinal or hilar adenopathy. However, it is more common to find some manifestations of mediastinal disease when
the lungs are involved.
Mediastinal large cell lymphomas can present as a mass in the thymus with or without lymph node involvement. Large
cell lymphoma of mediastinum is usually restricted to the intrathoracic region at the time of initial presentation. The
tumor has grossly invasive features; extension into pericardium, pleura, lung, sternum, and chest wall is common and
presentation with superior vena cava syndrome is frequent. Of tumors studied with cell markers, the majority has been
found to have B-cell nature, but T-cell malignancies are also present.
On CT scan, the enlarged nodes in any of the malignant lymphomas may be discrete or matted together, and their
edges may be well- or ill-defined. In general, they show only minor enhancement. Low density resulting from cystic
degeneration may be seen in both Hodgkin's and non-Hodgkin's lymphoma. In a study of radiologic findings of primary
mediastinal large-B-cell lymphoma in 43 patients, all but one lesion arouse in the anterior mediastinum, On CT scan,
large and lobulated anterior mediastinal masses were visible, averaging 10-cm in diameter. Low attenuation areas of
necrosis within the mass were seen in 44%, with calcification in two cases. Pleural and pericardial effusion were
present in about one-third.
A good response to radiation therapy and chemotherapy is the rule, but in many instances the tumor recurs massively
within the chest and spread to other sites, including peripheral lymph nodes. The presence of pleural effusion at
presentation is associated with poor outcome.