What Is Lymphoma?

The lymphatic system is shown in green in image

Lymphoma is a Heterogeneous Group of Cancers

“Lymphoma” is the general term for a heterogeneous group of cancers that arise from lymphocytes, a type of white blood cell (WBC).1,2 Lymphocytes are part of the lymphatic system, which is made up of a network of organs and vessels that carry lymph—a clear liquid composed of interstitial fluid, lymphocytes, bacteria, and proteins.3,4

Because the lymphatic system spans throughout the entire body, lymphoma can form and spread in almost any organ, though malignant cells often collect in the lymph nodes, liver, spleen, and other tissues.5

Is Lymphoma a Hematologic Malignancy or a Solid Tumor?

Unlike leukemia, which circulates in the blood, lymphoma can present in liquid form and/or grow as a solid mass, forming within an immune system structure like a lymph node or another organ containing lymphoid tissue.6 Lymphoma-causing lymphocytes can enter the circulation and be disseminated to almost any part of the body.2

Classification of Lymphoma

  • Lymphoma is classified broadly into Hodgkin’s lymphoma (HL) (~10% of lymphomas), and Non-Hodgkin’s lymphoma (NHL) (~90% of lymphomas)7
    • HL is characterized by the presence of large malignant cells called Reed-Sternberg cells7
    • NHL is the most common hematologic malignancy in the US8
  • NHL is further classified based on the type of lymphocyte of origin. ~90% of NHL arises from B cells, and the remainder arises from other types of lymphocytes, with 10% from T cells and <1% from NK cells9
  • NHL is made up of many different subtypes with heterogeneous clinical courses, which can be grouped into indolent (slow growing), aggressive (rapidly growing), or non-specific (not easily classified as indolent or aggressive) subtypes9

References: 1. Merck Manual. 20th ed. Lane KAG, ed. Rahway, New Jersey: Merck & Co., Inc. 2018. 2. National Cancer Institute. NCI Dictionary of Cancer Terms. https://www.cancer.gov/publications/dictionaries/cancer-terms. Accessed June 12, 2019. 3. Silverthorn DU. Human Physiology: An Integrated Approach. 4th ed. San Francisco, CA: Benjamin Cummings; 2007. https://ay12-14.moodle.wisc.edu/prod/pluginfile.php/48619/mod_resource/content/2/lymphatic_system.html. Accessed January 5, 2019. 4. Betts JG, et al. Anatomy & Physiology. 2nd ed. Houston, TX: OpenStax, Rice University; 2017. https://openstax.org/details/books/anatomy-and-physiology. Accessed January 5, 2019. 5. Cancer.net. Lymphoma – Non Hodgkin: Introduction. https://www.cancer.net/cancer-types/lymphoma-non-hodgkin/introduction. Accessed August 2, 2019. 6. Ruhl J, Adamo M, Dickie L, Negoita, S. Hematopoietic and Lymphoid Neoplasm Coding Manual (March 2018). National Cancer Institute. https://seer.cancer.gov/tools/heme/Hematopoietic_Instructions_and_Rules.pdf. Accessed January 5, 2019. 7. Leukemia & Lymphoma Society. Facts 2017-2018. https://www.lls.org/sites/default/files/file_assets/PS80_Facts2017-2018.pdf. Accessed August 2, 2018. 8. American Cancer Society. Cancer Facts and Figures 2018. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2018/cancer-facts-and-figures-2018.pdf. Accessed August 2, 2018. 9. Cancer.net. Lymphoma – Non-Hodgkin: Subtypes. https://www.cancer.net/cancer-types/lymphoma-non-hodgkin/subtypes. Accessed August 2, 2018.