Follicular lymphoma (FL) is one of the most common types of non-hodgkin lymphoma. Its incidence is second to only diffuse large B cell lymphoma. It is slightly more common in women and the the incidence increases with age. The incidence varies with geography and socioeconomic factors. Its is most common in Western Europe and Northern America.
Age: Follicular lymphoma is a disease of old age. The median age at diagnosis is 60-65 years. A paediatric variant, the paediatric follicular lymphoma, is seen in children but also in young adults. It has been recognised as a provisional entity in the 2016 WHO classification of lymphoid neoplasm.
Gender: Follicular lymphoma is slightly more common in women. The M:F ratio is 1:1.7. Paediatric follicular lymphoma has a male preponderance.
Geographic Variation: The incidence of follicular lymphoma is highest in North America and Western Europe. Incidence in Asia and Africa is lower.
Racial Variation: In the USA Caucasians have the highest risk. The risk in Asians and African-Americana is lower. The risk of FL in second generation Asians (Japaness and Chinese) immigrants to the USA is higher than their parents (Cancer Causes & Control 7:224-230; 1996). This suggests the role of environmental factors in the high incidence of FL in high risk regions of the world.
Association with Pesticides: Use of pesticides has been associated with increased risk of lymphoma. There is lesser information on the relation of subtypes of lymphomas. A recent study found a relation between lindane and diazinon and follicular lymphoma (PLoS One. 2014 Oct 22;9(10):e109332).
Molecular Risk Factors: Follicular lymphoma is characterised by the t(14;18) translocation that has a role in lymphogenesis. This translocation brings the BCL-2 gene under control of the IgH gene. This translocation has been found in as many as 46% of normal individuals (Int J Cancer. 2009 Feb 15;124(4):958-63). The prevalence of the translocation rises with age. Individuals with very high levels of cells carrying the translocation are at an increased risk for follicular lymphoma. The risk in individuals with one or more cell in 10,000 cells is 23 times more than individuals with lower levels of the transcript (J Clin Oncol 32:1347-55; 2014)