Histological variety of floral variant of follicular lymphoma

Follicular lymphoma: updates for pathologists

Follicular lymphoma (FL) is the most common indolent B-cell lymphoma and originates from germinal center B-cells (centrocytes and centroblasts) of the lymphoid follicle. Tumorigenesis is believed to initiate early in precursor B-cells in the bone marrow (BM) that acquire the t(14;18)(q32;q21). These cells later migrate to lymph nodes to continue their maturation through the germinal center reaction, at which time they acquire additional genetic and epigeneticabnormalities that promote lymphomagenesis. FLs are heterogeneous in terms of their clinicopathologic features. Most FLs are indolent and clinically characterized by peripheral lymphadenopathy with involvement of the spleen, BM, and peripheral blood in a substantial subset of patients, sometimes accompanied by constitutional symptoms and laboratory abnormalities. Diagnosis is established by the histopathologic identification of a B-cell proliferation usually distributed in an at least partially follicular pattern, typically, but not always, in a lymph node biopsy. The B-cell proliferation is biologically of germinal center cell origin, thus shows an expression of germinal center-associated antigens as detected by immunophenotyping. Although many cases of FLs are typical and histopathologic features are straightforward, the biologic and histopathologic variability of FL is wide, and an accurate diagnosis of FL over this disease spectrum requires knowledge of morphologic variants that can mimic other lymphomas, and rarely non-hematologic malignancies, clinically unique variants, and pitfalls in the interpretation of ancillary studies. The overall survival for most patients is prolonged, but relapses are frequent. The treatment landscape in FL now includes the application of immunotherapy and targeted therapy in addition to chemotherapy.

Follicular lymphoma

Follicular lymphoma (FL) is a systemic neoplasm of the lymphoid tissue displaying germinal centre (GC) B cell differentiation. FL represents ~5% of all haematological neoplasms and ~20-25% of all new non-Hodgkin lymphoma diagnoses in western countries. Tumorigenesis starts in precursor B cells and becomes full-blown tumour when the cells reach the GC maturation step. FL is preceded by an asymptomatic preclinical phase in which premalignant B cells carrying a t(14;18) chromosomal translocation accumulate additional genetic alterations, although not all of these cells progress to the tumour phase. FL is an indolent lymphoma with largely favourable outcomes, although a fraction of patients is at risk of disease progression and adverse outcomes. Outcomes for FL in the rituximab era are encouraging, with ~80% of patients having an overall survival of >10 years. Patients with relapsed FL have a wide range of treatment options, including several chemoimmunotherapy regimens, phosphoinositide 3-kinase inhibitors, and lenalidomide plus rituximab. Promising new treatment approaches include epigenetic therapeutics and immune approaches such as chimeric antigen receptor T cell therapy. The identification of patients at high risk who require alternative therapies to the current standard of care is a growing need that will help direct clinical trial research. This Primer discusses the epidemiology of FL, its molecular and cellular pathogenesis and its diagnosis, classification and treatment.

Classical Hodgkin lymphoma occurring in association with progressive transformation of germinal center

Progressive transformation of germinal center (PTGC) represents an asymptomatic persistent form of lymphadenopathy. We present a case of classical Hodgkin lymphoma occurring in association with PTGC. The patient was a 60-year-old woman who had noted swelling of the submandibular lymph nodes. Histopathologically, the enlarged lymph nodes appeared as multiple nodules with ill-defined and irregularly expanded germinal centers. Immunohistochemical studies indicated that the germinal center cells comprised B cells that were positive for CD10 and CD20, and negative for bcl-2. Enlarged vascular endothelial cells were present in the interfollicular areas. CD30-positive Hodgkin & Reed-Sternberg cells were seen between the interfollicular area and the mantle zone, and were surrounded by CD3-positive T-cells. In situ hybridization studies demonstrated no expression of Epstein-Barr virus-encoded small RNA in the Hodgkin & Reed-Sternberg cells. A diagnosis of classical Hodgkin lymphoma complicated by PTGC was made from the lymph node specimen.

Follicular lymphoma: stillSix characters in search of an author?

Follicular lymphoma (FL) is regarded as a distinct entity in the literature as well as in the 2008 edition of the WHO classification of tumours of haematopoietic and lymphoid tissues. Nevertheless, there are still several issues that are matters of controversy such as the grading system or the exact biological location of grade 3B FL. This makes FL somewhat like the Six characters in search of an author of Pirandello's comedy. Here, we revise the morphology and pathobiology of FL by highlighting both the areas remaining critical and future perspectives. This review was inspired by the reappraisal of Professor Lennert's personal archive that represents a unique legacy for the entire scientific community.

Recent Advances in Follicular Lymphoma: Pediatric, Extranodal, and Follicular Lymphoma in Situ

Follicular lymphoma is a relatively common B-cell lymphoma composed of follicle center B lymphocytes. Follicular lymphomas occurring in the pediatric population and in some extranodal sites exhibit particular clinicopathologic features and clinical behavior that are often distinct from adult nodal follicular lymphoma. A type of "in-situ" follicular lymphoma presents as intrafollicular neoplastic cells in a background of architecturally normal lymphoid tissue and may be difficult to recognize in routine sections. Accurate recognition of the morphologic variants and clinicopathologic subtypes of follicular lymphoma is important to avoid confusing them with other lymphomas and reactive processes; in addition, some of these subtypes of follicular lymphoma display unusually indolent clinical behavior that warrant their separation from "conventional" follicular lymphoma.

Immunoarchitectural patterns in follicular lymphoma: efficacy of HGAL and LMO2 in the detection of the interfollicular and diffuse components

Follicular lymphoma (FL) can exhibit variant histologic patterns that can lead to confusion with other B-cell lymphomas and reactive conditions. Diagnostic markers such as CD10 and BCL2 may be difficult to interpret in variant FL patterns, and are often diminished or absent in the interfollicular and diffuse components. We evaluated 2 recently characterized germinal center B-cell markers, human germinal center associated lymphoma (HGAL), and LIM-only transcription factor 2 (LMO2), in 127 FL patient biopsies (94 nodal, 33 extranodal), and correlated the findings with histologic pattern, cellular composition, grade, and additional immunostains (CD20, CD3, CD21, CD10, BCL2, and BCL6). Architectural patterns included predominantly follicular (75%) and follicular and diffuse components (25%); 10 cases showed marginal zone differentiation and 3 were floral variants. Eighty-nine cases were low grade (38 grade 1; 51 grade 2) and 38 were grade 3 (29 grade 3A and 9 grade 3B). HGAL had the highest overall sensitivity of detecting FL and was superior in detecting the interfollicular and diffuse components compared with BCL2, LMO2, CD10, and BCL6. All 28 cases that lacked CD10, expressed HGAL, and the majority also expressed LMO2. Our results show that HGAL and LMO2 are sensitive markers for FL diagnosis. The addition of HGAL and LMO2 to the immunohistologic panel is beneficial in the work-up of nodal and extranodal B-cell lymphomas and the efficacy of HGAL in detecting the follicular, interfollicular and diffuse components of FL is of particular value in the setting of variant immunoarchitectural patterns.

In situ follicular lymphoma associated with progressive transformation of germinal centers

The authors report here a case of in situ follicular lymphoma (FL) associated with progressive transformation of the germinal center (PTGC). A 39-year-old Japanese male developed a mass in the right cervical region. Biopsy of the enlarged lymph node led to a diagnosis of PTGC. Then, 5 years later, the lymphadenopathy recurred. The second biopsy specimens contained numerous germinal centers, including PTGC. Although most follicles were cytologically reactive, a few GCs appeared to be somewhat monotonous, composed predominantly of centrocytes and lacking mitotic figures and tangible body macrophages. Immunohistochemical studies demonstrated that these atypical GCs were CD10+, CD20+, and bcl-2+, with λ-light-chain restriction. A previous report emphasized the differential diagnostic problem between PTGC and the floral variant of FL. However, the present case indicated that in situ FL should be added to the list of differential diagnoses for PTGC.