Thoracic Imaging 2003 - Society of Thoracic Radiology

TUESDAY
182
Workshop A1: Lymphoma: Spectrum of Disease
Kitt Shaffer, M.D., Ph.D.
Assistant Chief of Radiology, Dana-Farber Cancer Institute
Introduction and Objectives
Lymphoma is actually a very heterogeneous collection of
disorders that can have a wide variety of clinical appearance and
imaging features. In general, lymphomas are classified into
either Hodgkin’s disease (HD) or non-Hodgkin’s lymphoma
(NHL). In both HD and NHL, the chest is a very frequent site
of involvement but the pattern of disease differs slightly
between the two disorders. In terms of incidence, HD and NHL
together make up about 5 percent of all newly diagnosed cancers
and about 5 percent of all cancer deaths. The incidence of
HD is similar to that of primary sarcomas while the incidence of
NHL is similar to that of pancreatic cancer. Both are much less
common that lung cancer. This workshop will review some
general principles of imaging of HD and NHL and will introduce
the complex topic of NHL classification, which is constantly
evolving as our understanding of the mechanisms of disease
expand. A brief review of some of the expected imaging
findings after treatment of lymphoma will also be presented.
After completing this workshop, participants should be more
familiar with typical and atypical imaging features of HD,
should be more aware of the various subtypes of NHL and some
of the newer categories based on immunophenotyping and genetic
analysis, and should be able to recognize common treatment
effects and complications of treatment of both HD and NHL.
Hodgkin’s disease
The typical appearance of thoracic disease in HD is an anterior
mediastinal mass without calcification or necrosis. Unlike
NHL, HD tends to spread contiguously, involving adjacent
nodal groups in an orderly manner. Lung involvement at diagnosis
is not uncommon in HD, but is always present in lung
adjacent to a hilar mass, indicating contiguous spread. Lung
involvement may be difficult to distinguish from atelectasis on
imaging studies. The commonest nodal groups involved by
NHL are first the anterior mediastinum followed by the right
paratracheal nodes and hilar nodes. Atypical appearances are
also possible in HD, and may include SVC syndrome, necrosis,
and calcification pre-treatment. Calcification in masses after
treatment are common.
Non-Hodgkins lymphoma
The imaging appearance of NHL is much more varied than
HD. Nodal involvement may often be discontinuous and overall
lung involvement is more common. Prognosis for NHL is also
worse than HD although there is a wide range from indolent
forms to more aggressive forms. In general, the indolent subtypes
are harder to cure but survival times are longer. The more
aggressive forms may kill the patient quickly but actually have
the best chance of long-term cure as most treatment modalities
(radiation and chemotherapy) depend on rapidly dividing cells,
which are seen in the more aggressive cell types.
Classification of NHL is a particularly complex topic and is
in constant flux. Many different systems have been used in the
past, most depending on histologic appearance of cells. More
current methods, such as the REAL classification system which
will be used in this presentation, attempt to integrate histology
with immunophenotype to approach a more pathophysiologically
based approach to classification. Some subtypes of NHL
(diffuse large cell, follicular, MALT) were well known from
prior systems but other subtypes (mantle cell, anaplastic large
cell, mediastinal large cell) are relatively new. Most of these
newer subtypes depend for diagnosis on either immunophenotyping
or genetic analysis, which were not included in older
classification systems.
Categories of NHL
Certain subtypes of NHL are so characteristic in histologic
appearance that they were well described and consistently diagnosed
even before the introduction of complex classifications
involving immunohistochemistry and cytogenetics. Among
these subtypes are diffuse large cell NHL, follicular NHL and
mucosal-associated lymphomas. Other subtypes are of more
recent origin, depending on more elaborate evaluations including
immunohistochemistry or analysis for genetic markers and specific
translocations. This includes anaplastic large cell NHL, mediastinal
large cell NHL, T-cell rich B-cell NHL and mantle NHL.
Diffuse large cell NHL is one of the more common subtypes
of NHL, and in the past probably included a very heterogeneous
group of disorders, some of which are now better discriminated
and reclassified into other categories, such as anaplastic large
cell or mantle cell NHL. Diffuse large cell NHL often involves
the chest and may include both nodal and extranodal disease. It
is typical of aggressive or high-grade NHL, which can have a
precipitous course, but is therefore often more responsive to
treatment and more amenable to cure. Most are of B-cell origin,
with about 20% demonstrating T-cell phenotype.
Follicular NHL is the prototype of indolent, low-grade lymphoma.
It is very difficult to cure, but patients may survive with
their disease for many years. Follicular NHL generally is restricted
to nodal disease and often has discontinuous involvement of
many nodal groups. Nodes may be small or bulky. If a particular
node or group of nodes suddenly enlarges, the possibility of transformation
to a higher grade tumor must be considered.
Lymphomas of the mucosal-associated lymphoid tissues
(MALT) have been well-known for some time and are generally
of the indolent variety. Most are of B-cell origin and most often
involve the lungs, stomach, salivary glands and lacrimal glands.
Almost any organ has been reported to give rise to MALT-like
lymphomas, including the bladder, the kidney, the uterus, breast,
and the thymus. Marginal zone lymphomas are neoplasms of
similar cell type occurring in nodes, involving the marginal
regions which surround germinal centers.
Anaplastic large cell NHL is a relatively recently described
category of NHL in which the neoplastic cells express the Ki-1
antigen, CD30. This same antigen is found on Reed-Sternberg
cells of HD as well as in activated T and B-cells. A characteristic
translocation is also usually present except in the cutaneous
form. Skin, lung and nodal involvement are common and the
course is often aggressive.
Mediastinal large cell NHL is a subtype of large cell NHL
that occurs specifically in the mediastinum and has a more
aggressive course. Tumor masses often contain considerable
sclerosis and the appearance can easily be mistaken for HD on
imaging, although signs of aggressive behavior, such as necrosis,
superior vena cava compression, and chest wall invasion, are
more commonly seen than in HD.