Excerpt from Hodgkin Disease, Thoracic

Synonyms, Key Words, and Related Terms: HD, Hodgkin lymphoma, Hodgkin's lymphoma, Hodgkin's disease, Epstein-Barr virus

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Background: Hodgkin disease (HD) is a lymphoma, which is a cancer of the lymph system characterized by the presence of abnormal large Reed-Sternberg cells in a background of lymphocytes, macrophages, fibroblasts, and granulocytes. Dr Thomas Hodgkin first described HD in 1832.

The lymphatic system is composed of lymph nodes, lymphatic channels, spleen, bone marrow, and thymus. As a result of the widespread presence of the lymphatic system throughout the body, HD can start almost anywhere; however, in this article, only thoracic involvement is addressed.

In the thorax, mediastinal involvement is most common. The nodular sclerosing histologic subtype of HD is the most common, and it has a predilection for the anterior mediastinum, especially the thymus. The diagnosis of HD must be based on tissue biopsy results because treatment strategies are based on the histologic type, the stage of disease, and the age and performance status of the patient. Imaging is essential for staging, for assessing the response to treatment, for diagnosing relapse, and for evaluating treatment-related disorders.

Pathophysiology: Etiology of HD remains unknown, but a strong association with the Epstein-Barr virus (EBV) exists. However, the presence of EBV is not specific and can be found in other malignancies.

At present, HD is not preventable because no definite cause has been identified.

Frequency:

In the US: According to the American Cancer Society, 7400 new cases of HD were estimated to occur in 2001 in the United States.
The incidence of HD in families of patients is increased, but the genetic nature is not certain, and it may be the result of exposure of family members to identical environmental hazards. The incidence is increased in patients who are immunocompromised, for example, in patients with AIDS and in organ transplant recipients.

Mortality/Morbidity: The aim of the treatment of HD is to cure the disease. More than 75% of newly diagnosed cases of HD can be cured with chemotherapy and/or radiation therapy. The prognosis depends on various factors; a few of these important factors include the presence of systemic symptoms, the stage of disease at presentation, the presence of large masses, and the treatment administered. Effective treatment has led to 1-, 5-, 10-, and 15-year survival rates of 93%, 82%, 72%, and 63%, respectively.

Sex: The male-to-female ratio is 1:1.5. In nodular sclerosing HD, females are affected twice as often as men, but in patients with nodular sclerosing HD, thymic involvement is more common in men.

Age: HD has a bimodal incidence. It is seen in adults aged 15-40 years and in persons older than 55 years.

Anatomy: Because mediastinal involvement of the lymph nodes is the most common manifestation of thoracic HD, knowledge of lymph node distribution and lymphatics in the thorax is important. A clear understanding of normal findings in the radiographic anatomy by using chest radiography (CXR) is pivotal to recognizing subtle enlargement of the lymph nodes.

On CXR of the left side, the normal aortopulmonary window is slightly concave, straight, or invisible. Any departure from this should be viewed with suspicion, and further investigations are needed. In the prevascular area, adenopathy is the most common cause for convexity of the aortopulmonary bay toward left lung.

On CXR of the right side, the azygous node lies variably in relation to the azygous vein as the vein passes forward above the right bronchus to enter the superior vena cava (SVC). This node is the lowest member of the group of right paratracheal lymph nodes. Any convexity in this region that has a greater part of its curvature above the right main bronchus probably should be regarded as abnormal. Low right prevascula .....