The Pax5 gene encodes the B-cell-specific activator protein which is a key regulator in development and differentiation of B-cell. We studied the expression of Pax5 in hematologic malignancies to evaluate the diagnostic utility as a B cell marker. Materials included 70 B cell lymphomas, 26 T cell lymphomas, 53 acute leukemias, and 6 multiple myelomas (MMs). Representative areas from the paraffinembedded tissues were selected for tissue microarray, and the expressions of Pax5 was immunohistochemically evaluated. Pax5 was strongly expressed in most of the B cell lymphomas; 44 of 47 diffuse large B cell lymphomas (93.6%), 15 of 16 marginal zone B cell lymphomas (93.8%), all 3 mantle cell lymphomas, 2 follicular lymphomas, and 2 Burkitt's lymphomas (100%). However, Pax5 was expressed in only one of 26 T cell lymphomas. Among leukemias, it was expressed in 10 of the 14 B acute lymphocytic leukemias (ALLs) (72.4%), but also in 3 of the 6 T ALLs (50%), 13 of the 26 acute myelogenous leukemias (AMLs) (50%) and in all 3 ALL arising in chronic myelogenous leukemias and 4 mixed B ALL and AML. In MMs, Pax5 was negative in all cases. We concluded that Pax5 is very useful B cell marker in classification of lymphomas, but not of acute leukemias.
B-Lymphocytes/pathology/physiology ; DNA-Binding Proteins/genetics/*metabolism ; Human ; Leukemia/classification/*metabolism/pathology ; Lymphoma, Non-Hodgkin/classification/*metabolism/pathology ; Support, Non-U.S. Gov't ; Tonsil/cytology/metabolism/pathology ; Transcription Factors/genetics/*metabolism ; Tumor Markers, Biological/*metabolism

OBJECTIVETo describe the relative frequency, morphologic features, immunophenotype and clinical data of different types of B-cell non-Hodgkin lymphoma (B-NHL) and to evaluate the practical application of the 2001 World Health Organization (WHO) classification of lymphoid neoplasms.

METHODS369 documented cases of B-NHL were further subtyped according to the 2001 WHO classification of lymphoid neoplasms, on the basis of hematoxylin and eosin staining, immunohistochemistry and in-situ hybridization techniques.

RESULTSAmongst the 369 cases of B-NHL studied, 353 cases could be further classified into 11 subtypes. Diffuse large B-cell lymphoma, extranodal marginal zone lymphoma and follicular lymphoma were the commonest subtypes, accounting for 51.2% (189 cases), 14.9% (55 cases) and 10.6% (39 cases) of all cases respectively. Tumors in lymph nodes were seen in 158 cases (42.8%) and in extra node in 211 cases (57.2%). B-cell prolymphocytic leukemia and hairy cell leukemia were not identified. When comparing the diagnosis based on morphologic examination alone with the diagnosis based on both morphology and immunophenotype, there was a 80% concordance rate. Immunohistochemical study was helpful in reaching the correct diagnosis in many cases and could improve the overall diagnostic accuracy by about 20%.

CONCLUSIONSAmongst cases of B-NHL, diffuse large B-cell lymphoma is the commonest subtype, followed by MALToma and follicular lymphoma. While morphologic examination forms the basis for lymphoma diagnosis, immunohistochemical study also plays an important role in further subtyping. A combination of both modalities are sufficient for arriving at an accurate diagnosis in most cases of B-NHL, in keeping with the recommendation of the 2001 WHO classification of lymphoid neoplasms.

Adolescent ; Adult ; Aged ; Aged, 80 and over ; Antigens, CD20 ; metabolism ; CD79 Antigens ; metabolism ; Child ; Female ; Humans ; Immunohistochemistry ; Leukosialin ; metabolism ; Lymphoma, B-Cell ; immunology ; pathology ; Lymphoma, B-Cell, Marginal Zone ; immunology ; pathology ; Lymphoma, Follicular ; immunology ; pathology ; Lymphoma, Large B-Cell, Diffuse ; immunology ; pathology ; Lymphoma, Non-Hodgkin ; classification ; immunology ; pathology ; Male ; Middle Aged ; World Health Organization

OBJECTIVETo identify the immunohistochemical patterns of follicular dendritic cell (FDC) meshwork and Ki-67 labeling index in small B-cell lymphomas (SBLs) and their significance in differential diagnosis.

METHODSSixty-eight cases of SBLs were included collected from November 2008 to June 2012. The patterns of FDCs and Ki-67 expression were studied on paraffin sections by CD21, CD23 and Ki-67 immunohistochemistry. The characteristic staining patterns of FDCs and Ki-67 expression among different SBLs were analyzed statistically.

RESULTSThe age of SBL patients ranged from 28 to 85 years with a mean of 55.2 years. The male to female ratio was 1.2:1. Fifty-five cases involved only lymph nodes (80.9%), and the remaining cases involved multiple extra-nodal sites. Histological classification of the cases was made according to the 2008 WHO lymphoma classification criteria: 22 were low-grade follicular lymphomas (FLs, including grade 1 and grade 2), 19 marginal zone lymphomas (MZLs), 17 mantle cell lymphomas (MCLs), and 10 chronic lymphocytic leukemia/small lymphocytic lymphomas (CLL/SLLs). FDC meshwork limited to the central part of neoplastic follicles was characteristic for FL (90.9%, 20/22). The germinal center FDC meshwork was destroyed primarily at periphery in MZL (14/19). The absence or scattered FDC clusters were typical of SLL/ CLL. Irregular FDC was seen in 7/17 of MCL, while 7/17 MCL displayed FDC pattern similar to that of CLL/SLLs. The pattern of FDCs was a significantly diagnostic feature in distinguishing the four types of SBLs (P < 0.01). Ki-67 was also a statistically significant parameter (P < 0.05) with decreasing labeling index as the following: MCL, FL, SLL and MZL. Ki-67 showed scattered pattern in germinal centers with loss of polarity in FLs. MZL presented uniformly scattered positive pattern in interfollicullar areas. Ki-67 staining was uniform in MCL, but its labeling index varied from 5% to 90%. The Ki-67 index was higher in the morphological "proliferation centers" of all CLL/SLLs.

CONCLUSIONImmunohistochemical staining patterns of FDC meshworks and Ki-67 labeling index offer a significant discriminatory power in the differential diagnoses among SBLs.

Adult ; Aged ; Aged, 80 and over ; Antigens, CD20 ; metabolism ; Dendritic Cells, Follicular ; pathology ; Diagnosis, Differential ; Female ; Humans ; Immunohistochemistry ; Ki-67 Antigen ; metabolism ; Leukemia, Lymphocytic, Chronic, B-Cell ; metabolism ; pathology ; Lymphoma, B-Cell ; classification ; metabolism ; pathology ; Lymphoma, B-Cell, Marginal Zone ; metabolism ; pathology ; Lymphoma, Follicular ; metabolism ; pathology ; Lymphoma, Mantle-Cell ; metabolism ; pathology ; Lymphoma, Non-Hodgkin ; metabolism ; pathology ; Male ; Middle Aged ; Receptors, Complement 3d ; metabolism ; Receptors, IgE ; metabolism ; Retrospective Studies

Antibodies, Monoclonal, Murine-Derived ; therapeutic use ; Antineoplastic Agents ; therapeutic use ; Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Bleomycin ; therapeutic use ; Cyclophosphamide ; therapeutic use ; Dacarbazine ; therapeutic use ; Doxorubicin ; therapeutic use ; Hodgkin Disease ; drug therapy ; Humans ; Lymphoma ; classification ; drug therapy ; pathology ; Lymphoma, Large B-Cell, Diffuse ; drug therapy ; Lymphoma, Large-Cell, Anaplastic ; drug therapy ; metabolism ; Lymphoma, Non-Hodgkin ; drug therapy ; Prednisone ; therapeutic use ; Receptor Protein-Tyrosine Kinases ; metabolism ; Rituximab ; Vinblastine ; therapeutic use ; Vincristine ; therapeutic use