What Is Follicular Lymphoma (FL)?

Follicular Lymphoma

Reproduced with permission from Atlas of Haematological Cytology

FL is an incurable, indolent (slow-growing) non-Hodgkin lymphoma (iNHL) defined by the proliferation of malignant germinal center B-lymphocytes (centrocytes and centroblasts).1,2 See Pathogenesis of FL.

Follicular lymphoma cells include small to medium-sized germinal center B cells called centrocytes and large B cells called centroblasts, which are present in mostly intact lymphoid follicles.3 The number of centroblasts per high-power field (HPF) may be counted and used to estimate the aggressiveness of the disease.3 See Histology of Follicular Lymphoma.

Graphic of clinical presentation of FL

Lymphadenopathy

Clinical Presentation of FL

Patients with FL typically present with asymptomatic lymphadenopathy (eg, lymph node disease, manifesting as small to medium superficial nodes).4,5 Few patients experience B symptoms (recurring fever, drenching night sweats, or significant weight loss) or an altered performance status.4,6 See Clinical Presentation of Follicular Lymphoma.

The diagnosis of FL follows a similar process for diagnosing other types of NHL, including a physical exam, laboratory workup, histology, cytogenetic analysis, immunophenotyping, molecular profiling, and patient imaging.7 See Initial Diagnostic Workup of Follicular Lymphoma.

US Statistics: FL Incidence

FL is the second most common type of NHL in the US, with approximately 13,000 new cases of FL diagnosed per year in 2019.8-10 The median age at diagnosis is 63 years.10

  • In 2019, an estimated 74,200 new cases of NHL will be diagnosed, with FL accounting for ~20% of all cases11
  • Approximately 2.7 out of every 100,000 people have a new diagnosis of FL each year (based on 2012–2016 registry)12
  • Per statistical models for analysis, rates of new FL diagnoses on average have been falling (~2% each year) between 2006 and 2016, while rates of death appear to be stable12

Genetic Mutations in FL

  • Approximately 90% of cases of FL have a reciprocal chromosomal translocation that involves chromosomes 14 and 18.13 A reciprocal chromosomal translocation is a genetic abnormality in which pieces from two different chromosomes trade places with each other.14 The t(14;18) translocation is thought to be an early event in FL pathogenesis, and the accumulation of other mutations are required for lymphomagenesis.13 See Pathogenesis of FL.

References: 1. Lymphoma Research Foundation. About Lymphoma: Follicular Lymphoma. https://www. lymphoma. org /aboutlymphoma/nhl/fl/. Accessed January 5, 2019.   2. Kridel R, Sehn LH, Gascoyne RD. Pathogenesis of Follicular Lymphoma. J Clin Investig. 2012;122(10):3424-3431. 3. Takata K, Miyata-Takata T, Sato Y, et al. Pathology of follicular lymphoma. J Clin Exp Hematop. 2014;54(1):3-9. 4. Salles GA. Clinical features, prognosis and treatment of follicular lymphoma. Hematology 2007:216-225. http://asheducationbook.hematologylibrary.org/ content/2007/1/216.full. Accessed February 10, 2019. 5. Freedman A. Follicular Lymphoma: 2018 Update on Diagnosis and Management. Am J Hematol. 2018;93:296-305. 6. Leukemia and Lymphoma Society. Non-Hodgkin Lymphoma Signs and Symptoms. https://www.lls.org/lymphoma/non-hodgkin-lymphoma/signs-and-symptoms. Accessed February 13, 2019. 7. Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for B-Cell Lymphomas V.4.2019. © National Comprehensive Cancer Network, Inc. 2019. All rights reserved. Accessed July 10, 2019. To view the most recent and complete version of the guideline, go online to NCCN.org. NCCN makes no warranties of any kind whatsoever regarding their content, use or application and disclaims any responsibility for their application or use in any way. 8. Leukemia & Lymphoma Society. Non-Hodgkin Lymphoma. https://www.lls.org/sites/default/ files/ file_assets/nhl.pdf. Accessed January 5, 2019. 9. National Cancer Institute. SEER Cancer Statistics Review 2008-2014: Table 19.29. https://seer.cancer.gov/archive/csr/1975_2015/results_merged/sect_19_nhl.pdf. Accessed July 1, 2019. 10. National Cancer Institute. SEER Cancer Statistics Facts: Non-Hodgkin lymphoma. https://seer.cancer.gov/statfacts/html/nhl.html. Accessed February 10, 2019. 11. Miller KD, Nogueira, L, Mariotto AB, et al. Cancer Treatment and Survivorship Statistics, 2019. CA Cancer J Clin. 2019;0:1-23. 12. National Cancer Institute. SEER Cancer Statistics Facts: NHL – Follicular Lymphoma. https://seer.cancer.gov/statfacts/html/follicular.html. Accessed June 12, 2019. 13. Leich E, et al. Follicular lymphomas with and without translocation t(14;18) differ in gene expression profiles and genetic alterations. Blood. 2009 114:826-834. 14. National Cancer Institute. NCI Dictionary of Cancer Terms. https://www.cancer.gov/publications/dictionaries/cancer-terms. Accessed June 12, 2019.