Diagnosis of Pediatric-Type Follicular Lymphoma in Young Adults (Own Data)

Abstract

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.