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.
Currently used indicators for this include the diseases: 1) histology; 2) subtype; 3) predicted indolence and potential for transformation; and 4) extent of disease as measured by clinical examinations, bone marrow biopsy to determine bone marrow involvement, and PET/CT imaging of the chest, abdomen, pelvis, and any areas outside of these regions if physical examination suggests involvement. Some suggested guidelines using these parameters to indicate the prognosis and need for treatment in FL include:
The WHO criteria using histological grade (see previous section): Patients with Grades 1, 2, and 3A disease are predicted to have the same low risk prognosis that is seen in cases of typical FL while patients with grade 3B disease are predicted to have the high risk prognosis typical of t-FL. The Follicular Lymphoma International Prognostic Index (FLIPI): FLIPI uses the following criteria: age ≥60 years; Ann Arbor disease stage III (i.e. lesions located both above and below the thoracic diaphragm) or IV (i.e. disseminated lesions involving one or more non-lymphatic organs); blood hemoglobin <12 gram/deciliter; serum lactose dehydrogenase level above normal; and involvement of >4 lymph nodes. Patients positive for 0–1, 2, or ≥3 of these factors are classified as in low, intermediate, and high risk group, respectively, and after treatment with regimens that include rituximab have 2 year predicted progression free survivals of 84, 72, and 65%, respectively, and overall survivals of 98, 94, and 87%, respectively. The FLIP2 index.