General Information / Anatomy / Function / Statistics

• The lymphatic system is a network of small vessels called "lymphatics" which resemble blood vessels
• Lymphatics return fluid from the tissues of the body to the bloodstream
• Part of the body defense against infection
• Most of the cells which circulate in the lymphatic system are white blood cells called lymphocytes.  When a lymphoma develops, the malignant cell is a lymphocyte.
• Lymphatic tissue is found as well in many organs of the body, particularly the spleen, liver, bone, skin, marrow and intestine
• The seventh most common cause of cancer deaths
• The  fifth most common cancer diagnosed in men or women

Cancers of the Lymphatic System

• Abnormal cells appear as congregations which enlarge the lymph nodes, form solid tumors in the body, or rarely, like leukemia, circulate in the blood
• May be fast growing or very slow growing depending on the type

Classification

• Divided into two large groups
  • Hodgkin's disease
  • Non-Hodgkin's lymphomas
• Hodgkin's disease can be subclassified into five subtypes, however, the treatment approach is the same for each of them
• Non-Hodgkin's lymphomas are divided into two main groups; low grade lymphomas which tend to grow slowly and aggressive histology lymphomas which tend to grow faster. These can be further classified into approximately twenty different subtypes, based on an international classification scheme called the World Health Organization Classification.
• Under a microscope, lymphoma tissue can resemble normal lymph tissue but always has characteristic changes indicating the malignancy
• Pathologists may disagree about the exact type of lymphoma being observed and an expert in the area of lymphoma pathology must be consulted to determine a final diagnosis
• If there is any doubt as to the diagnosis, patients should ask that their tissue samples (slides) be reviewed by several experienced pathologists. Sometimes a second biopsy is necessary for proper diagnosis

T-Cell Lymphoma

General Information / Anatomy / Function / Statistics

• 90% of lymphomas are B-cell. Thus, T-cell lymphoma is rare.
• All lymphomas arise from normal lymphocytes (immunity regulating white blood cells) in the body
• Two types of lymphocytes:
  • B-cell: derived from bone marrow cells
  • T-cell: derived from thymus, a special gland in the central part of the chest
• B-cell lymphocytes make antibodies
• T-cell lymphocytes regulate the B-cell lymphocytes
• Lymphomas can arise from either B- or T-cell lymphocytes. This ancestry can be demonstrated with some special tests in the laboratory
• T-cell and B-cell lymphomas often differ in
  • Places in the body where they occur
  • Appearance under the microscope
  • Response to treatment
• In general, T-cell lymphomas are more difficult to treat and have a greater chance of recurring
• Occasionally T-cell lymphomas show a predisposition to attack the skin
• A very rare form of T-cell lymphoma has been found due to a virus. If the characteristics of your lymphoma suggest this type of lymphoma (high calcium in blood, bone and skin lesions, lymphoma cells in blood and bone marrow) your doctor will send special blood tests to check for the virus.

Revised April 2000