[1473] Immunoarchitectural Patterns in Follicular Lymphoma: Efficacy of HGAL and LMO2 in the Detection of the Interfollicular Component

SF Younes, A Beck, RA Warnke, IS Lossos, R Levy, Y Natkunam. Stanford Medical Center, Stanford, CA; University of Miami, Miami, FL

Background: Follicular lymphoma (FL) can exhibit variant histologic patterns that lead to confusion with other B-cell lymphomas and reactive conditions. Diagnostic markers such as CD10 and BCL2 may be difficult to interpret in variant FL patterns and are often diminished or lacking in the interfollicular component. We characterized variant FL patterns and the efficacy of two new germinal center B-cell markers, HGAL and LMO2, in that setting.
Design: A total of 111 FL patient biopsies (84 nodal, 27 extranodal) from Stanford Pathology files were evaluated for histologic pattern, cellular composition, grade and the following immunostains: CD20, CD3, CD21, IgM, IgD, PD-1, CD10, BCL2, HGAL and LMO2.
Results: Architectural patterns included 83 (74.8%) predominantly follicular and 28 (25.2%) follicular and diffuse. Five cases showed marginal zone differentiation and 2 were floral variants. Signet ring features were seen in 3, tingible body macrophages in 2 and 1 showed Reed-Sternberg-like cells. Sclerosis was seen in 43 and prominent vasculature in 18 cases. Seventy-seven cases were low grade (33 grade 1; 44 grade 2) and 34 were grade 3. Immunohistologic findings are summarized in table 1.

Table 1
MarkerStaining PatternOverall Sensitivity
Follicular onlyFollicular and interfollicularPositive Proportion (%) [95% CI]
HGAL11/101 (10.9%)83/101 (82.2%)94/101 (93.1%) [86.4 – 96.6%]
CD1027/110 (24.5%)60/110 (54.5%)87/110 (79.1%) [70.6 – 85.6%]
BCL27/109 (6.4%)79/109 (42.5%)86/109 (78.9%) [70.3 – 85.5%]
LMO20/103 (0%)70/103 (68%)70/103 (68.0%) [58.4 – 76.2%]

Conclusions: Our results show that HGAL and LMO2 are sensitive markers for FL diagnosis. HGAL had the highest sensitivity (93%) and was superior in detecting the interfollicular component. We have previously shown that HGAL and LMO2 are specific for lymphomas derived from germinal center B-cells and seldom expressed in marginal zone lymphomas (Natkunam et al., 2005, 2007 and Salama et al., 2009). All 23 cases that lacked CD10, expressed HGAL, and the majority also expressed LMO2. The addition of HGAL and LMO2 to the immunohistologic panel is of benefit in the work-up of nodal and extranodal B-cell lymphomas. The efficacy of HGAL in detecting both the follicular and interfollicular components of FL is of particular value in the setting of variant immunoarchitectural patterns.
Category: Hematopathology

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 199, Monday Morning


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