[1281] Angioimmunoblastic T-Cell Lymphoma with Hyperplastic Germinal Centres (Pattern I): Clinicopathological and Immunohistochemical Study of 10 Cases
M Rodriguez-Justo, A Attygalle, P Munson, G Roncador, MA Piris. University College London Hospital, London, United Kingdom; Royal Marsden Hospital, London, United Kingdom; Spanish National Cancer Centre, Madrid, Spain
Background: AITL is an aggressive T-cell lymphoma which natural history is not fully understood. Up to 16% of cases show a pattern of hyperplastic germinal centres (pattern I) and the majority of these cases are initially misdiagnosed as reactive hyperplasia. The correct identification of AITL - pattern I remains a challenge and the aim of this study is to characterize phenotypically this variant with the use of follicular T-cell (TFH) markers PD1 (antibody NAT-105) and CXCL13.
Design: AITL cases from files of the Spanish National Cancer Centre and University College London were reviewed and 10 cases with pattern I were identified. Cases were stained for CD3, CD4, CD8, CD30, CD21/CD23, CD10, CXCL13 and PD1. EBV status was assessed by LMP1 and/or EBER and PCR for IgH and TCR was performed to evaluate clonality. Clinical and demographic data were obtained from referring physicians. 21 lymph node biopsies with reactive lymphoid hyperplasia (including HIV lymphadenopathy) were used to compare PD1 and CXCL13 expression in reactive vs. neoplastic cases.
Results: 10/10 (100%) cases showed strong positive PD1 staining in the 
outer zone
of the lymphoid follicle, perifollicular area and around high endothelial veins. CXCL13 showed variable staining in neoplastic cells in 8/10 cases. In 10/10 cases CD21/CD23 highlighted only a subtle expansion of follicular dendritic cells. In reactive hyperplasias, PD1+ve cells were found in the germinal centre with a few T-cells in the interfollicular T-cell zone. EBV was found in 9/10 cases. Clinically 6/7 cases presented with stage IIIB/IV B and in 2/10 cases consecutive biopsies showed progression to classical patterns II and III (diffuse).
Conclusions: PD1 has useful diagnostic utility in the distinction and identification of AITL with hyperplastic germinal centres in conjunction with the appropriate clinical setting. CXCL13 is variable expressed and its diagnostic utility is limited. PD1 identifies neoplastic cells in the outer zone of the lymphoid follicle, suggesting that AITL 
pattern I may originate from TFH cells in the outer zone, in harmony with previous immunological studies. As the majority of cases in our series presented clinically with stages IIIB/IVB, progression from pattern I to patterns II and III may represent histological transformation rather than clinical progression.
Category: Hematopathology
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 192, Wednesday Morning