On the other hand, expression of certain markers, such as memory B-cell marker CD27, molecules related to B-cell homing such as chemokine (C-C motif) ligand 20 (CCL20) and mucosal vascular addressin cell adhesion molecule 1 (MAdCAM-1), lack of activation-induced cytidine deaminase (AID), and variable immunoglobulin heavy chain gene (VH) usage suggest a genetic similarity of PI-FL with gastric mucosa-associated lymphoid tissue lymphoma, but different from systemic nodal FL [13, 17–20]. This evidence concerns the gene AICDA and gastric mucosa-associated lymphoid tissue lymphoma.