Median Channel Fluorescence (MCF) for Transferrin Receptor 1 (CD71) Show Poor Correlation with Ki-67 Staining Pattern and Histological Grade in Follicular Lymphoma (FL)
N Bures, I Auer, J Luider, A Mansoor. University of Calgary & Calgary Laboratory Services (CLS), Calgary, AB, Canada
Background: Stratification among Follicular lymphoma (FL) is based on histologic grade, in-spite of high inter-observor variation. Ki-67 is the prime marker for cell proliferation and is indirectly associated with FL grade. Ki-67 scoring is subjective and can be influenced by infiltrating non-neoplastic cells. Transferrin receptor 1 (TFRC1) or CD71, is also closely associated with cell proliferation. We hypothesized that objectivity in Flow-cytometric (FC) evaluation of CD71 expression may show better association with histological grade in FL compared to Ki-67.
Design: H&E stained formalin-fixed, paraffin-embedded (FFPE) tissue sections (4 µm) were reviewed independently by two Hematopathologist. Diagnosis of FL was established and FL was graded according WHO classification (2008). Grade discrepancy was resolved by consensus. A standardized IHC staining, employing heat -induced antigen retrieval technique (EDTA buffer at pH 8.0), utilizing automatic immunostainer (Ventana, Tucson, AZ) was used for Ki-67 (1:50, MIB-1). Ki-67 staining was scored on 4 tier system in area of maximum staining (average of 10 HPF). Fresh homogenized cell suspension was stained with Five colour antibody cocktail (IgG-FITC, CD71-PE, CD10-ECD, CD38-PC5, and CD19-PC7) and analyzed on a FC500 analyzer (Beckman Coulter-CA). CD71 median channel fluorescence (MCF) was established on B-cells (CD10+19+ co-expressing events where possible). Chi-square and Mann-Whitney U test were used for statistical analysis.
Results: 27 pts (43-87 yrs, median 64 yrs; M:F 1.5:1) were included. Low grade (grade 1-2) was noted among 20 (74%) while high grade (grade 3A& 3B) was observed in 7 (26%) pts. Ki-67 staining pattern showed 1+ among 15 of 27 (56%) pts; 2+ in 3 of 27 (11%) pts; 3+ among 2 of 27 (7.4%) pts and 4+ among 7 of 27 pts (26%). MFI among low grade FL ranged between 1.2-11.2 (mean 4.5; median 3.2) while among high grade FL MFI ranged 4.17-101 (mean 29.6, median 20.7). Proliferation index by CD71 or Ki67 did not show a significant correlation with FL grade using the chi square (p>1). The Mann-Whitney U test showed an estimated probability of 67% of Ki67 with FL grade, while the estimated probability for CD71 with FL grade was 40%.
Conclusions: These results suggest that CD71 expression by flow cytometry or Ki 67 by IHC are not reliable markers compared to the histological grade of FL. Howeever, Ki 67 from our study shows a better correlation to grade than CD71.
Monday, March 22, 2010 1:00 PM
Poster Session II # 162, Monday Afternoon