The malignant cells in marginal zone B-cell lymphoma may form follicular structures but commonly proliferate in the marginal zone rather than germinal center of lymphoid tissues. These malignant cells often show features of monocytes or plasma cells. Mantle cell lymphomas show monotonous, medium-sized lymphocytes, monocytes, and atrophied germinal centers; unlike FL, the malignant lymphocytes in this disease are positive for Cyclin D1 by immunohistochemistry staining. Small lymphocytic lymphomas are composed of nodular structures with small- to medium-sized malignant cells surrounding immature lymphocytes and immunoblasts. The malignant cells in this disease, unlike FL, stain positive for CD5 and CD23. Treatment and prognosis
FL is typically a slowly growing lymphoma with an overall median life expectancy for treated patients of 10–15 years with many cases of it waxing and waning in the size of their lesions and rare cases of it remitting spontaneously. These considerations favor the use of observation over intervention in patients whose particular form of FL has a favorable prognosis or who are intolerant to aggressive treatments. However, most cases of FL have a less favorable prognosis at some stage of their disease and will therefore require intervention. There is little consensus regarding the guidelines to be used to define the prognosis and treatment for FL at its presentation or during its course..
For example, laboratory studies show that: 1) follicular dendritic cells, fibroblastic reticular cells, and T helper cells provide growth and survival signals to neoplastic follicular B-cells; 2) neoplastic follicular B-cells recruit regulatory T cells that act to suppress immune responses to them; 3) the cytotoxic T-cells which normally kill neoplastic cells become dysfunctional in the presence of neoplastic follicular cells that are embedded in this multicellular environment; and 4) bone marrow stromal cells directly support the growth of neoplastic follicular cells. Reduced levels of immune-infiltration has been shown to be strongly associated with early progression of disease. Presentation and course
In situ follicular lymphoma
FL is commonly preceded by but uncommonly progresses to ISFL, an asymptomatic disorder that usually is discovered in tissues which are biopsied for other reasons. FL lymphoma may be diagnosed in the uncommon  cases in which individuals with ISFL are found to have FL on follow-up examinations. Similarly, individuals with >1 in 10,000 circulating lymphocytes containing the t(14:18)q32:q21) translocation are at increased but still small risk of developing FL and being diagnosed as having FL on follow up examinations. Follicular lymphoma
FL commonly presents as an otherwise asymptomatic enlargement of lymph nodes 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.