[1227] Differential Staining of Phospho-AKT in Normal Marginal Zone Cells Versus Marginal Zone B Cell Lymphoma

S Kemp, KA Rizzo. Indiana University, Indianapolis, IN

Background: Marginal zone B cell lymphomas (MZL) are subclassified as nodal marginal zone B cell lymphoma, extranodal marginal zone B cell lymphoma of MALT type (MALT lymphoma) and splenic marginal zone lymphoma (SML). Due to the non-specific immunophenotype in MZL, investigations have focused on new diagnostic and prognostic markers. AKT(PKB) plays a significant role in cell survival and apoptosis and is activated via phosphorylation. Few reports show that phospho-AKT is seen in certain hematopoietic malignancies. We undertook a study to analyze the expression of phospho-AKT in normal marginal zone B cells versus B cells in marginal zone B cell lymphoma.
Design: 21 cases were retrieved and included 5 cases of non-malignant spleens, 1 case of SML, 9 cases of MALT lymphoma and 5 cases of MZL in a lymph node. H&E and immunostains performed on paraffin sections were reviewed and marginal zone cells were analyzed for phospho-AKT staining. The percent of overall positive cells were measured on a 0-4 scale (0= 0 cells, 1 = 1-25%, 2 = 26-50%, 3 = 51-75%, 4 = 76-100%) and the intensity of staining was analyzed on a 0-2 scale (0 = no staining, 1 = minimal, 1.5 = moderate, 2 = marked).
Results: The age range was between 1 and 79 years old. The location of the MALT lymphomas included the stomach (7 cases), breast (1 case) and thyroid (1 case). Two of the stomach MALT lymphoma cases were from the same patient, the first biopsy was H.pylori positive; the subsequent one was H. pylori negative. The marginal zone cells in 4 of the 5 non-malignant splenic cases were completely negative, while one case showed minimal staining (1) in less then 25%(1) of the cells. In the marginal zone lymphoma cases, 11 of the 15 cases (73%) scored a 4 for overall positive cells, 1 case scored a 3 (7%) and 4 cases scored a 2 (27%). Statistical analysis via student t-test showed a statistical significance in the number of positive cells between the malignant and non-malignant groups (p=1.77 x 10^-8). Analysis of the staining intensity of phospho-AKT within the malignant group showed a large majority of the malignant cases contained moderate to marked (1.5-2) staining intensity(87%, 13 of 15 cases).
Conclusions: Our study shows differential positive staining of phospho-AKT between normal and malignant marginal zone B cells. Analysis of the activation of the AKT pathway in marginal zone lymphomas may lead to diagnostic immunohistochemical markers as well as insights into activation/upregulation of signaling pathways.
Category: Hematopathology

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 137, Tuesday Morning