Lymphoma: Overview and Risk Factors

Lymphomas are cancers of the lymphatic system, which includes the lymph nodes, spleen, and other organs, including the lung, liver, or gastrointestinal tract. In general, lymphomas are highly treatable, and over 50 percent of individuals survive beyond five years.

Lymphomas are classified as either non–Hodgkin’s or Hodgkin’s lymphoma. Non–Hodgkin’s lymphoma is the sixth most common cause of cancer–related death in the United States, and the death rate has more than doubled since 1950. Untreated, the most aggressive forms have a very poor prognosis, with survival rates measured in weeks or months. However, with appropriate treatment, many of the aggressive types are curable. On the other hand, the less aggressive types may not need immediate treatment, but they are generally not considered curable.

Hodgkin’s lymphoma has a survival rate of more than 85 percent. There are several different types, which are all generally treated similarly and have comparable outcomes.

The symptoms of both categories of lymphoma include fever, night sweats, weight loss, fatigue, and itching. Painless enlargement of lymph nodes is common and, in some cases, may press upon surrounding organs and cause further symptoms (e.g., an enlarged lymph node that puts pressure on the throat may cause coughing).

Risk Factors

Non–Hodgkin’s Lymphoma

• Increasing age: Although the disease occurs in all age groups, the incidence rises dramatically after age 50.
  
• Family history: Individuals with one or more affected first–degree relatives have twice the usual risk.
  
• Exposure history: Herbicides and other chemicals have been linked to an increased risk.
  
• Immunodeficiency disorders: These include immune deficiency states (such as HIV infection), chronic immunosuppression (such as chronic steroid use), and autoimmune diseases.
  
• Infectious agents: Viral and bacterial infections have been associated with an increased risk of specific types of lymphoma.

Hodgkin’s Lymphoma

• Age: Peak incidence occurs in young adults (ages 15 to 35) and in individuals older than 50.
  
• Male gender: The condition is more common in males, especially in children and younger adults.
  
• Geography: Incidence increases in areas with high industrial development.
  
• Genetics: There is nearly a 100–fold increased risk in identical twins and as much as a seven–fold increased risk among siblings of Hodgkin’s disease patients. It remains unclear whether the increased familial risk is due to a genetic susceptibility or common environmental exposures.
  
• Infectious agents: Several associations have suggested a link between Epstein–Barr virus and Hodgkin’s disease. Other infectious etiologies may play a role.
  
• Breast–feeding: In several studies, breast–feeding has been associated with a reduced risk of Hodgkin’s disease.