Pathology

Welcome to the Lymphoma section. This section is divided into four subsections: Introduction, Hodgkin's Disease, Non-Hodgkin's Lymphoma, and Clinical Aspects of Lymphoma

The Lymphoma Introduction, section contains basic definitions and an overview of lymphoma classification.

The FAB classification of myeloid leukemias does not correlate with clinical or theraputic outcomes.

Additional clinical aspects of leukemia may be found with the discussion of the pathology.

Malignant lymphomas (ML) are cohesive malignant proliferations of lymphocytes arising in lymph nodes and in lymphoid tissue of various organs (extranodal). Malignant lymphomas may also be thought of as neoplasms of the immune system. Rarely, the term lymphoma is used to refer to a malignant proliferation of true histiocytic cells, but more on that later.

Lymphoma should be distinguished from leukemia, although this is not always easily done.

The malignant lymphomas constitute a heterogeneous group of neoplasms arising from the immune system and primarily involving lymphoid cells.

ML is classified based on 1) the cell type and 2) the architectural (growth) pattern. In this way, two large categories: the Hodgkin's and the Non-Hodgkin's lymphomas are defined.

For a review of the morphology and immunology of normal lymphocytes and lymph nodes, click the "Review" button below. You can return to this page and proceed with the Introduction to Lymphoma by clicking the "Lymphoma" button in the Review section.

In lymphoma, normal lymph node architecture is distorted or effaced by the proliferating malignant lymphoid cells.

The effacement of nodal architecture may be either diffuse (left) or follicular (center). The follicular pattern may evolve into a diffuse pattern (right). The growth pattern is observed at low magnification while high magnification is used for assessment of cell type (next card). Note the growth or extension of lymphoma outside of the capsule. This is typical of lymphoma.

In malignant lymphoma the proliferative cell is usually monomorphous (one type of cell); in reactive conditions, the proliferations are polymorphous (multiple types of cells). In this illustration we see a proliferation of small lymphocytes in a diffuse pattern or malignant lymphoma, small lymphocytic (ML,SL).

Here we see a case of malignant lymphoma, small lymphocytic (ML,SL). Note the proliferation of small lymphocytes in a diffuse pattern.

Here we see a follicular pattern of growth with follicular structures growing beyond the capsule. Looking inside one of the follicles you see a predominance of one cell type-in this case small cleaved lymphocytes. Thus, you can make a diagnosis of malignant lymphoma, follicular, small cleaved cell (ML,SCC, follicular).

Here is an actual case of malignant lymphoma, follicular, small cleaved cell (ML,SCC, follicular).

Note the follicular pattern of growth. At right is a high magnification view of a follicle with a predominance of one cell type-in this case small cleaved lymphocytes.

If these were normal follicles in a reactive node, what would you expect to see in the follicle at high magnification?

Right! You would expect a polymorphous mixture of lymphocyte cell types in the germinal center of a reactive node. Reactive lymphoid hyperplasia is characterized by enlargement of the lymph node, hyperplasia of follicular (germinal) centers, increased numbers of histiocytes in sinusoids, and interfollicular hyperplasia of lymphocytes and plasma cells (often with more immunoblasts).

This example of Reactive lymphoid hyperplasia is characterized by hyperplasia of follicular (germinal) centers. Note the variablilty in the size of the follicles and the presence of a mantle zone in the reactive node. Most important is the mixture of large and small lymphocytes; plasma cells (green) and "tingible body" macrophages (blue) in the reactive germinal center.

A 59 year-old woman complains of a painless lump in her neck that she first noticed about 4 months ago. It has enlarged only slightly since she first noted it. The surgeon said other nearby nodes were involved as well. You are the pathologist. What do you tell the surgeon?

The area in the box is shown at right.

One more point! We said there were two large categories of lymphoma: the Hodgkin's and the Non-Hodgkin's lymphomas. These two types of lymphoma are distinguished by differing morphologic and clinical features.

Hodgkin's lymphomas are characterized by the presence of giant bilobed or multinucleate Reed-Sternberg cells in a reactive appearing cellular background. In contrast, the non-Hodgkin's lymphomas generally consist of a uniform proliferation of cells. More on R-S cells in the discussion of Hodgkin's disease.

Lymphoma is the 6th most common malignancy in the United States. There were an estimated 43,000 new cases of lymphoma in the United States in 1990. Non-Hodgkin's lymphoma accounted for 35,600 cases (83%) and Hodgkin's for 7,400 (17%) cases.

The incidence of Non-Hodgkin's lymphoma progressively increases with age (peak approximately 60 years). In contrast, a bimodal peak is seen with Hodgkin's disease - with a peak between ages 20-29, a plateau between 30-55 and a second rise after age 55.

Lymphoma is more frequent (1.5:1) in males than females for both Hodgkin's disease and non-Hodgkin's lymphoma.

The major clinical manifestation of malignant lymphoma is painless lymph node enlargement. Such nodes are usually firm or rubbery, often multiple and fixed in place,

Systemic symptoms include fever, malaise, night-sweats, weight loss, and pruritis. As lymphoma progresses, spread may occur to spleen, liver, bone marrow, and other organs.

Common primary sites of lymphoma include cervical, supraclavicular, mediastinal, axillary, periaortic, and inguinal lymph nodes.

Common extranodal sites of lymphoma include the gastrointestinal tract, CNS, skin, spleen, bone marrow, pharyngeal tissues, salivary glands, thymus, and lung among others.

The physical presence of disease and the presence or absence of symptoms are the measures for the respective pathologic and clinical staging of lymphoma.