A t(14;18) Negative Nodal Diffuse Follicular Lymphoma with 1p36/TNFRSF14 LOH Detected by Cytogenomic Microarray Analysis

Abstract

Abstract Introduction/Objective Among the already described variants of nodal follicular lymphoma (FL), there is a variant with diffuse growth pattern with a predilection to involve the inguinal lymph nodes and peculiar immunohistochemical and molecular characteristics. The diffuse growth pattern is manifested by the complete absence of follicles without a follicular/dendritic meshwork (negative CD21 and CD23). This variant was first described by Katzenberger in 2009. It is distinguished from other variants by CD23 expression, lack of t(14;18)/ IGH::BCL2 rearrangement, and chromosome segment 1p36 deletion or TNFRSF14 mutations. Methods/Case Report A 43-year-old Caucasian male presented with a lump in his left groin, noted by him after exercising and sought surgical opinion to rule out inguinal hernia. CT- scan of abdomen and pelvis showed a well circumscribed 4.3 cm lymph node in the left groin region. Histological analysis of the lesion depicted a lymph node with a predominantly diffuse and focally vaguely nodular proliferation effacing the architecture. Numerous centrocytes admixed with occasional centroblasts averaging <15/HPF. The neoplastic cells are positive for CD20, PAX5, CD10, BCL6, CD23 and BCL2, and are negative for CD5 and cyclin D1. The CD21 highlights few residual germinal centers at the periphery of the lymph node. The proliferative (Ki67+) index is approximately 30-40%. Flow cytometry demonstrates CD10 positive, kappa monoclonal B cell population (20% of total). FISH analysis was negative for both IgH/BCL2 t(14;18) rearrangement and TNFRSF14 (1p36) Deletion. However, cytogenomic microarray analysis (CMA) revealed genomic imbalances and copy neutral Loss of Heterozygosity over 1p36 in a mosaic state representing about 40% of the cells, which notably encompasses PRKC2, SKI, TNFRSF14, PRDM16, TP73 and PRL22 genes. The findings are consistent with a final diagnosis of diffuse follicular lymphoma variant, WHO grade 1-2 of 3. Results (if a Case Study enter NA) N/A Conclusion The copy neutral Loss of Heterozygosity of 1p36 region which contains TNFRSF14 gene was detected by CMA only. Undoubtedly, CMA results can play a pivotal role in identifying copy neutral Loss of Heterozygosity or small regions deletions or gains that can be missed by conventional cytogenetics and FISH studies and subsequently establishing diagnosis and prognostic stratification of hematologic neoplasms.