Usefulness of HGAL and LMO2 Immunohistochemistry in the Identification of Follicular Lymphomas of the Non-Gastric Gastrointestinal Tract

Abstract

We studied the sensitivity of 2 relatively new markers of germinal center B-cell origin, namely human germinal center-associated lymphoma (HGAL) and Lim-only transcription factor 2 (LMO2), in the identification of follicular lymphomas (FLs) of the nongastric gastrointestinal (GI) tract. We retrospectively reviewed cases of endoscopically derived primary, nongastric GI lymphomas including FL, grade 1 or 2, and extranodal marginal zone lymphoma (ENMZL) of mucosa-associated lymphoid tissue, classified based on morphologic features and immunohistochemical analysis. HGAL and LMO2 immunohistochemical stains were then prospectively performed in each case. When discrepant immunohistochemical results were obtained, fluorescent in situ hybridization was performed for t(14;18) IGH/BCL2 and IGH rearrangement using a dual color fusion and a dual color break-apart probe, respectively. All but one of the CD10-negative ENMZL cases were negative for both HGAL and LMO2. One case originally classified as ENMZL was positive for both HGAL and LMO2. Fluorescent in situ hybridization did not detect either t(14;18) IGH/BCL2 or IGH rearrangement in this case. It is likely, based on positivity of 2 established germinal center B-cell markers, that this represents a FL which was originally misclassified as an ENMZL based on CD10 negativity. Of the cases of FL (all CD10 and/or BCL-6 positive), 8 (80%) were positive for both HGAL and LMO2. Although HGAL and LMO2 did not demonstrate an increased sensitivity in the identification of FL of the nongastric GI tract in this series, they still were helpful in the reclassification of one of our cases, and may therefore be useful adjuncts in the identification of FL of the nongastric GI tract.