| Objective: To study the morphologic, immunophenotypic and molecular genetic alterations in follicular lymphoma and explore their significance of diagnosis and differential diagnosis in follicular lymphoma.Methods: Fifty-five cases formalin-fixed, paraffin-embedded tissue blocks of FL,28 cases of other small B-cell lymphoma, 16 cases of diffuse large B-cell lymphoma (DLBCL), and 10 cases of reactive follicular hyperplasia (RFH) were constructed into tissue microarry, and stained with antibodies against CD20, BCL2,BCL6,CD10,CD23 and Ki-67 by Envision techniques; Using traditional polymerase chain reaction (PCR) and DNA sequencing technique to detect t(14;18) translocation of all follicular lymphoma and RFH. House-keeping gene (?)-actin was used to detect the quality of DNA. And semi-nest PCR technique had been used to detect colonel rearrangement of the immunoglobulin heavy chain (IgH): Paraffin-embedded samples of 20 cases of follicular lymphoma, 28 other small B-cell lymphoma cases and 4 cases of reactive follicular hyperplasia were identified by dual-color FISH. The result was compared with the traditional PCR technique.Result: (1) In all RFH cases, the expression of CD10 and BCL-6 was limited in the germinal center B-cells (GCCs). Reactive GCCs did not express BCL2．The Ki-67 labeling index of GCCs was over 70% in all RFHs. In FLs, both follicular and interfollicular neoplastic cells expressed CD10 (65．4%) and BCL-6 (70．3%). Notably, neoplastic GCCs of FLs expressed BCL-2(85．1%). The Ki-67 index was lower (30-40%) in all FLs, and cellular polarization in the follicles is absence in follicular lymphoma. Neither CD10 nor BCL-6 expression was observed in SLL, MCL or MZL. But 81．8% SLLs, 77% MCLs, and 75% MZLs expressed BCL-2．The Ki-67 index was lower in these three tumors (30-40% ). Inconsistent expression of CD10 (25%) and BCL-6 (31．2%) was noticed in DLBCL cases. 18．7% cases co-expressed these two markers. 50% DLBCLs were positive for BCL-2 and Ki-67 index of all the cases varied from low to high. (2) In 55 FL cases,β-actin DNA was detected in 50 cases of 55 FL (90 %). Clonal IgH rearrangements were detected in 34(68%) cases. Among the 49 case of nodul FL, t(14; 18) translocation were detected in 15 cases, 14 cases in MBR and one case in mcr. t(14;18) translocation were not detected in all 6 cases of extranodul FL. PCR product had been confirmed by the sequence analysis. (3) Among the cases of t(14;18) positive, 13/15(86．6%) expressed BCL2 , 13/15(86．6%) expressed CD10, 12/15(80%) expressed BCL6．In the t(14;18) negative cases, 26/29(89．6%) expressed BCL2, 19/29(65．7%) cases expressed CD10, and 25/29(86．2%) cases expressed BCL6．Expression of CD10, BCL6 and BCL2 is no correlated with t(14;18) positive. (4) 6 cases of exyranodul FL, expressed BCL-2(5/6) , CD 10(3/6) and BCL6(4/6) . Follow up data were available in 5 patients and all of them had good recovery. (5) t(14;18) translocation, was detected in 16(80%) of 20 paraffin-embedded FL by FISH. t (14;18) translocation was not found in 4 cases of reactive follicular hyperplasia by FISH. Compare of FISH and PCR studies, FISH is superior to PCR in detecting t (14;18) translocation using paraffin-embedded tissue samples.Conclusion: (1) Follicular lymphoma and other small B-cell lymphoma and RFH have their distinct histological feature and different composed cell, both of which can be used in diagnosis and differential diagnosis. (2) CD10 and BCL-6 may play a critical role to distinguish FL from RFH and other small B-cell lymphomas. The staining pattern of BCL-2 and Ki-67 may be helpful for differential diagnosis between FL and RFH, but it can not distinguish FL from other small B-cell lymphomas. (3) EFL arising from the other sites is similar in terms of morphology and immunophenotype with FL occurring in lymph node. However, Like cutaneous FL, the tumors were lack of t( 14; 18) translocation, and have good prognosis. It should be differentiated from mucosa-associated lymphoid tissue lymphoma. Immunohistochemical staining for BCL6 and CD10 is helpful in making a correct diagnosis. (4) Expression of CD10 is not correlate to t(14;18) positive . Clonal IgH rearrangements of FL were detected lower compare to other small B-cell lymphoma. The frequency of PCR-detected t(14;18) translocation were 34．1%, this method is less sensitive. (5) The detection of t (14;18) translocation using paraffin-embedded by FISH may be helpful in diagnosis of FL. FISH is superior to PCR in sensibility and easy to operate. It can be application to detect molecular genetic abnormal of paraffin-embedded tissue. |
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