in the neck, armpit, groin, femoral canal, or other sites in individuals (median age 65) without a known history of ISFL or abnormal numbers of circulating t(14:18)q32:q21-conatianing lymphocytes. These enlargements may have been present for months to years and during this time waxed and waned in size. Less commonly, FL presents as extra-nodal masses in the skin, thyroid gland, salivary gland, breast, testicles. spleen, liver, and/or lung. Regardless of the type of presentation, FL is usually (~80% of cases) at an advanced stage at diagnosis as indicated by involvement of the bone marrow (50% to 70% of cases), multiple lymph nodes in different parts of the body, and/or other tissues. A minority (<33%) of FL patients present with B symptoms, i.e. recurrent unexplained fevers, recurrent night sweats, and/or weight loss ≥10% in the past 6 months. Generally, the disease has an indolent and prolonged course with a median life expectancy of 15–20 years: a large percentage of patients die from other causes than their FL disease. However, each year, including the early years after diagnosis, some 2-3% of FL cases transform to t-FL; Median survival has been ~4.5 years after the onset of this transformation. There are less common subtypes of FL that differ not only in their presentation but also in their histopathology, genetic abnormalities, and course. These subtypes, which are now (i.e. primary gastrointestinal tract FL) or may in the future (pediatric-type FL) be considered distinctive diseases, are: Duodenal-type follicular lymphoma Duodenal-type follicular lymphoma (DFL) was initially considered to be a type of Primary gastrointestinal tract (GI tract) follicular lymphoma (PGTFL), i.e. a follicular lymphoma in which GI tract lesions were prominent parts of the disease. However, a subset of PGTFL cases had lesions that were localized to the duodenum and other parts of the small intestine usually without involving other parts of the GI tract or tissues outside of the GI tract. This contrasts with the other cases of PGTFL which were systemic diseases involving a wide range of GI tract and non-GI tract tissues. Consequently, the World Health Organization (2017) removed the localized disease from the primary gastrointestinal tract follicular lymphoma category, reclassified it as a distinct disease entity, and termed it duodenal-type follicular lymphoma. DFL is most often an asymptomatic disease that is diagnosed on endoscopic examination of the GI tract conducted for other reasons. Less commonly, it presents with vague abdominal symptoms. In one