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Follicular lymphoma is composed of clonal germinal center B cells. It shows a follicular pattern lacking mantle zones, with a network of interfollicular dendritic cells. Transformation to more aggressive lymphomas is documented, but the only connections to mantle cell lymphoma are described cases of composite lymphoma consisting of these 2 entities. We discuss here a case of a lymph node harboring CD20, CD10, BCL2, BCL6, cyclin D1, CD5, Ki67, and SOX11 with CD21, showing an almost intact network of dendritic cells in one part of a lymph node, and CD20, CD5, SOX11, BCL6, cyclin D1, CD10, Ki67, and CD21 cells restricted to the mantle area in another part of the same lymph node. Both parts of the lymph node had BCL2 rearrangement, a lack of t(11:14)(q13;q32), the presence of SOX11 expression, and the same clonal band. The described case suggests heterogenous development of small cell lymphomas and indicates the possibility of differentiation regression.

In modern clinical laboratory routine, cell analysis by flow cytometry means help in setting up the diagnosis by determination of B-lymphocyte clonality and thus separation of benign and malignant lymphoproliferative diseases. The aim of this study was to assess the value of cytologic diagnosis and adequacy of the material obtained by fine needle aspiration (FNA) of lymph nodes for flow cytometry analysis in cases of benign lesions and primary malignant lesions of lymph nodes. In addition, the aim was to determine B-lymphocyte clonality in different groups of benign and malignant lymph node lesions. The study was based on medical documentation, cytologic smears of FNA lymph node samples and results of flow cytometry immunophenotyping. A total of 239 patients were included over a one-year period. Patients were classified according to cytologic findings in the groups of non-Hodgkin's lymphoma of B cell origin (55%), benign lymphoproliferative disease (22%), undefined group of monomorphic population of lymphatic cells (16%), and the rest in the group of non-Hodgkin's non B cell origin. Study results showed FNA to be an appropriate method for obtaining sufficient numbers of cells for analysis by flow cytometry because there was no inadequate samples in our study group. In some cases of monomorphic lymphoid cell population, cytologic diagnosis was limited to small cell lymphomas, so determining the clonality by flow cytometry is crucial in separating malignant from benign lymphoproliferative disease. It is concluded that FNA associated with the flow cytometry method is a simple and safe method in the diagnosis of lymphoproliferative disease.

Flow cytometry immunophenotyping (FCI) has an important role in the clinic work-up of fine needle aspirates (FNAs) of lymph nodes. Its standardization has been defined by proposed analytical protocols and procedures used to assure proper analytical results also in those non-routine samples. In Institute of Clinical Chemistry, "Merkur" University Hospital, FCI is accredited method according to laboratory accreditation standard ISO 15189. According to this laboratory accreditation standard, participation in external quality assessment (EQA) programs is a prerequisite for assuring integrity and quality of the entire laboratory process. A critical analysis of our institutional experience in the feasibility of FCI of the material obtained by FNA of lymph nodes with suspected lymphoma represented the purpose of the study. During an eight-year period in Institute of Clinical Chemistry, "Merkur" University Hospital, a total of 1295 FNA analysis was done, 245 of them with a possible diagnosis of B-cell Non-Hodgkin lymphomas (B-NHL) formed the basis of the study. Lymphocytes were isolated on density gradient according to Boyum et al. The average feasibility of FNAs for FCI analysis was 86% (ranged 78-93%). An acceptable total cell number in FNAs for FCI analysis (4257) was established. In total population of respondents statistical significances in expressions of cellular antigens CD3, CD5, CD22, CD23, CD19 and CD5 on B-cells (CD5+CD19+) between patient's with final diagnosis of benign, reactive lymphoid proliferations and patient's with diagnosis of B-NHL were found. EQA results analysis showed that all results were either inside target values (X +/- 1SD) or inside accepted values (X +/- 2SD). Compatibility of the restriction of immunoglobulins light chains determinated by FCI and cytomorphology diagnosis depends on the choice of criterion values of the light chains ratio which determine the monoclonality. According to the matrix of shares of all classified data of retained neural network, ranges of diagnostic sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and prevalency of 82%, 72%, 93%, 48%, and 72% were produced. As a conclusion, FCI is a reliable methodology for phenotyping FNAs of lymph nodes with suspected B-NHLs detecting their clonality easily.