[1449] Immunophenotypic Subsets of Peripheral T Cell Lymphomas

Stephanie M McGregor, M Kamran Mirza, John Anastasi, James W Vardiman, Elizabeth Hyjek, Sandeep Gurbuxani. University of Chicago Medicine, Chicago, IL

Background: The current classification of peripheral T-cell lymphomas is based primarily on morphology, anatomic location and clinical features. Unlike B-cell lymphomas, there is little correlation with the cell of origin and stages of normal T-cell development and a significant proportion of peripheral T-cell lymphomas are classified as “not otherwise specified” (PTCL-NOS). The current study was undertaken to determine the frequency of expression of markers associated with follicular T-helper cells (TFH, BCL6 and PD-1) and the innate-like T-cells called natural killer T-cells (NKT, PLZF) in peripheral T-cell lymphomas classified as PTCL-NOS, Anaplastic Large Cell Lymphoma (ALCL), ALK- and the cytogenetically defined ALCL, ALK+.
Design: We used a tissue microarray that included 26 biopsies from PTCL-NOS, 11 biopsies from ALCL, ALK- and 13 biopsies from ALCL, ALK+. Only specimens with well-defined tumor infiltrate were included. The presence of tumor was confirmed using an H&E stained section of the TMA. Histologically normal tonsil, lymph node and thymus specimens were used as controls. Immunohistochemistry was performed in the clinical immunohistochemistry laboratory at the University of Chicago. Lymphomas were scored as positive when 20% or more of the tumor cells showed expression with appropriate subcellular localization – i.e nuclear for BCL6 and PLZF and membranous for PD-1.
Results: Frequency of expression for the various antigens evaluated is described in Table 1.

Table 1: Frequency of Antigen Expression
Diagnosis (n)PD-1+ (%)BCL6+ (%)PD-1+ BCL6+ (%)PLZF+ (%)PLZF+ PD-1+ BCL6+ (%)
PTCL-NOS (26)65625080
ALCL, ALK- (11)937900
ALCL, ALK+ (13)15858238

Conclusions: As reported previously, co-expression of BCL6 and PD-1 was observed frequently in all three subtypes of PTCL's evaluated. In contrast, co-expression of PD-1 and BCL6 was observed more frequently in PTCL-NOS when compared to ALCL, ALK- or ALCL, ALK+. Furthermore, BCL6 and PD1 co-expression was exclusive of PLZF expression in PTCL-NOS and might help identify a unique subtype of peripheral T-cell lymphoma that is derived from an NKT-cell. Future studies will determine the prognostic significance of the TFH phenotype based on co-expression of multiple TFH antigens and better define the cell of origin for PLZF-positive PTCL's.
Category: Hematopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 274, Tuesday Afternoon


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