Hodgkin Lymphoma

Overview

Hodgkin Lymphoma is a neoplasm of probable B-cells characterized by the morphological presence of the Reed-Sternberg Cell and a prototypical metastatic pattern that begins in the supra-diaphragmantic lymph nodes and spreads contiguously along lymphatic chains.

Epidemiology

Hodgkin Lymphoma follows a bimodal age distribution with one peak between age 15-35 and another in those older than 60.

Morphology

Hodgkin Lyphoma is defined by the presence of characteristic Reed-Sternberg cells which are thought to be the actual neoplastic cells of this disease. Based on a variety of immunophenotypic and genetic evidence, it is thought that these cells originate from B-cells. Interestingly, these neoplastic cells may be fairly rare within the tumor mass, which may be largely composed of a non-neoplastic infiltrate of mostly inflammatory cells. Five histological variants of Hodgkin Lymphoma have been described which display different clinical prognoses. Following a description of the Reed-Sternberg cell, we briefly describe the four histological variants

Reed-Sternberg (RS) Cells are large cells that display multiple nuclei with prominent eosinophilic nucleoli. The classic RS cell displays two mirror-image nuclei that gives the cell an owls-eye appearance. Although diagnosis of Hodgkin Lymphoma does not absolutely require the presence of RS cells, their identification is pathognomonic for the disease.

This is the most common subtype of HL and is characterized by the presence of collagenous bands which divide the tumor into distinct nodules. RS cells are relatively rare in this subtype.

This subtype is characterized by plentiful RS cells and a diverse inflammatory background which includes lymphocytes, eosinophils, plasma cells, and macrophages

As the name suggests, this subtype is characterized by a prominant infiltrate of small, mature-looking lymphocytes. Classic RS cells are relatively rare.

This subtype is characterized by a relative paucity of inflammatory infiltrate and frequent RS cells which may be seen as confluent sheets in tumors. This subtype is associated with the worst prognosis.

Clinical Consequences

Hodgkin Lymphoma usually arises in a single lymph node, most commonly in the supra-diaphragmatic axial lymph node chains, which include the cervical, mediastinal, or para-aortic nodes. The unique characteristic of Hodgkin Lymphoma, compared to Non-Hodgkin Lymphoma, is its tendency to spread in an ordered continguous pattern from its site of origin. In some patients, release of inflammatory cytokines can result in B-type symptoms, discussed below. The anatomic geography of tumor-involved areas and the presence of B-symptoms is used for staging and prognostic purposes.

Painless lymphadenopathy of the supra-diaphragmatic lymph nodes, especially the cervical lymph nodes, is the most common presenting symptom of Hodgkin's disease. Disease usually spreads contiguously along lymphatic chains and over time will spread to sub-diaphragmatic nodes, then to the spleen, and finally the liver. Neoplastic cells can also spill outside of the lymphatic system to extralymphatic sites. Some patients display "B-symptoms" which include fevers, drenching night sweats, and weight loss. A generalized pruritis is also occasionally observed.

Patients are clinically staged according to the Ann-Arbor classification system into four general categories depending on the extent of tumor spread. Each stage is given an A or B modifier depending on the absence of B-symptoms (A) or their presence (B).
Stage I: Involvement of a single lymph node region or a single extralymphatic organ or site
Stage II: Involvement of two or more lymph node regions on the same side of the diaphragm alone or with involvement of limited, contiguous extralymphatic organ or tissue
Stage III: Involvement of lymph node regions on both sides of the diaphragm, which may include the spleen or limited, contiguous extralymphatic organ or site or both.
Stage IV: Multiple or disseminated foci of involvement of one or more extralymphatic organs or tissues, with or without associated lymph node involvement.

Prognosis in HL is largely a function of clinical stage with more advanced stages and the presence of B-symptoms being unfavorable. Histological subtype is not thought to play a major role in prognosis although the Lymphocyte Depleted subtype is relatively unfavorable.

Treatment

Treatment of Hodgkin Lymphoma represents a high point of modern oncology and early stage treatment is often curative. Treatment typically involves a combination of chemotherapy as well as radiation to the torso in a "mantle"-like distribution, termed "Mantle Radiation".

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