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Background. Grade 3 follicular lymphoma (FL) is a heterogenetic group of tumors. The selections of patients with similar characteristics of the tumor process is important for classification 3 grade forms of FL and risk stratification, as well as for the development of new therapeutic approaches. Different morphological, immunohistochemical and cytogenetical characteristics of the tumor result in different clinical forms of the disease. Aim. To describe the clinical, morphological, immunohistochemical and cytogenetical characteristics of grade 3 FL and evaluate their prognostic value for R-CHOP-21 chemotherapy. Materials & Methods. We performed retrospective and prospective analysis of morphological, immunohistochemical and genetical characteristics of 93 primary patients with grade 3 FL (21-78 years, median 53 years, women to men - 1:1.4) admitted to National Medical Hematology Research Center from years 2001 to 2016. Morphological and immunohistochemical assessment of the affected lymph nodes and bone marrow biopsy material was performed. Data obtained from the standard cytogenetic and FISH assessment were compared to identify the BCL2 rearrangement. Results. We proposed an algorithm for differential diagnosis of the 2 types of grade 3 FL: de novo FL (n = 22) and transformed FL (n = 21). De novo grade 3 FL had the immunophenotype of CD10- in 19 (86 %) cases, MUM1++ (monomorphically) in 19 (90 %), and BCL-2 in 5 (22 %). It was characterized by the absence of the BCL2 rearrangement (n = 22, 100 %) and bone marrow involvement (n = 14, 67 %) and/or bone marrow involvement (n = 7, 100 %). Third grade FL transformed from grades 1 or 2 had was CD10+ (n = 19, 90 %), MUM1+ (heterogeneously, n = 16, 76 %) or MUM1-(n = 4, 19 %), BCL-2+ (n = 20, 95 %) and had BCL2 rearrangement (n = 19, 90 %). Small cell bone marrow involvement was observed in 71 % of cases, whereas large cell involvement was seen predominantly in de novo FL (p = 0.06). The analysis showed that 5-year relapse-free survival in patients with grade 3 de novo FL after R-CHOP-21 therapy was 87 % compared to 16 % with transformed FL (p = 0.06) for the median 41 months of follow up. Conclusion. We described the morphological, immunohistochemical and cytogenetical characteristics of grade 3 de novo FL and grade 3 FL, transformed from grades 1 or 2. The described variants show different sensitivity to immunochemotherapy.

Aim. Pathomorphological, immunophenotypical and clinical characteristics of a new clinico-morphological form of pediatric-type follicular lymphoma (FL) in young adults discovered in 2008 (WHO classification). Background. FL is a heterogeneous disease according to its morphological, immunophenotypical and molecular-genetic characteristics. FL de novo includes transformed FL, FL without t(14;18), FL with diffuse growth associated with del(1p.36) and TNFRSF14 mutation. Pediatric-type FL in young adults is poorly studied; and it is especially interesting because of its clinical diversity and molecular-genetic heterogeneity of FL, in general. Methods. Biopsy materials taken from 5 patients (aged 18-25 years; median age: 22 years; the female/male ratio 3:2) were included in the study; all patients were examined, diagnosed and treated in the Hematology Research Center over the period from 2012 to 2016. Clinical stage I with isolated involvement a palatine tonsil or an inguinal lymph node was diagnosed in 4/5 patients; clinical stage II with involvement of a palatine tonsil and cervical lymph node was diagnosed in 1/5 patients. Morphological, immunophenotypical and FISH tests were performed with paraffin blocks. Results. The morphological pattern was typical for FL 3B (n = 2) and FL 3 with blastoid nucleus morphology (n = 3). Immunophenotypical features demonstrated an intermediate position between FL 3 de novo and transformed FL 3. No BCL-2 rearrangement was detected in any observation. Conclusion. The comparison of our data on characteristics of pediatric-type FL with those published in the literature demonstrated that lack or weak expression (< 30 % of tumor substrate cells) of MUM1 was the key feature of the experimental group of young adults with pediatric-type FL. This, in turn, indicates the absence of IRF4 rearrangements and possible presence of other genetic abnormalities. The clinical, morphological, and immunophenotypical characteristics broaden the FL heterogeneity spectrum in young adults.